Impressora C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.Collections;
using System.Collections.Generic;
using Escolheimp;
using System.Windows.Forms;

namespace Impressora
{
    public partial class Form1 : Form
    {
        Semaphore sem = new Semaphore(3, 3);
        delegate void SetTextCallback(string texto);
        delegate void SetTextCallback2(string texto);
        delegate void SetTextCallback3(string texto);
        Mutex mutex = new Mutex();
        string[] velocidade = new string[] { "NA", "NA", "NA" };
        string A;
        string B;
        string C;
        string[] estado= new string[] { "livre", "livre", "livre" };

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {


            for (int i = 0; i < 3; i++)
            {
                Thread newThread = new Thread(new ThreadStart(impr));
                newThread.Name = String.Format("Thread{0}", i + 1);
                newThread.Start();
            }
        }

        private void impr()
        {
            while (true)
            {
                sem.WaitOne();

                mutex.WaitOne();
                for (int i = 0; i < 3; i++)
                {
                    if ((i==0)&&(this.estado[0] == "livre"))
                    {

                        this.estado[0] = "ocupado";
                        //dictionary.Add("rapido", 0);
                        this.B = Thread.CurrentThread.Name;
                        velocidade[0] = this.B;
                        break;

                    }
                    if ((i == 1) && (this.estado[1] == "livre"))
                    {

                        this.estado[1] = "ocupado";
                        this.A = Thread.CurrentThread.Name;
                        //dictionary.Add("medio", 1);
                        velocidade[1] = this.A;
                        break;

                    }
                    if ((i == 2) && (this.estado[2] == "livre"))
                    {

                        this.estado[2] = "ocupado";
                        this.C = Thread.CurrentThread.Name;
                        //dictionary.Add("lento", 2);
                        this.velocidade[2] = this.C;
                        break;

                    }

                }


                mutex.ReleaseMutex();


                imprime(velocidade);

                mutex.WaitOne();
                librera(velocidade);
                mutex.ReleaseMutex();
                Thread.Sleep(200);
                sem.Release();

            }
        }

        private void librera (string[] spped)
        {
            string[] speed = spped;

            if (speed[0]==Thread.CurrentThread.Name)
            {
                this.estado[0] = "livre";
                this.velocidade[0] = "NA";
                //this.dictionary.Remove("rapido");
            }
            if (speed[1] == Thread.CurrentThread.Name)
            {
                this.estado[1] = "livre";
                this.velocidade[1] = "NA";
                //this.dictionary.Remove("medio");
            }
            if (speed[2] == Thread.CurrentThread.Name)
            {
                this.estado[2] = "livre";
                this.velocidade[2] = "NA";
                //this.dictionary.Remove("lento");
            }
        }
        private void imprime(string[] spped)
        {
            string[] speed = spped;
            if (speed[0] == Thread.CurrentThread.Name)
            {
                Thread.Sleep(500);
                if (this.txtTexto1.InvokeRequired)
                {
                    SetTextCallback e = new SetTextCallback(attcont);
                    this.Invoke(e, new object[] { Thread.CurrentThread.Name });

                }

            }
            if (speed[1] == Thread.CurrentThread.Name)
            {
                Thread.Sleep(600);
                if (this.txtTexto1.InvokeRequired)
                {
                    SetTextCallback2 f = new SetTextCallback2(attcont1);
                    this.Invoke(f, new object[] { Thread.CurrentThread.Name });

                }

            }
            if (speed[2] == Thread.CurrentThread.Name)
            {
                Thread.Sleep(700);
                if (this.txtTexto1.InvokeRequired)
                {
                    SetTextCallback3 g = new SetTextCallback3(attcont2);
                    this.Invoke(g, new object[] { Thread.CurrentThread.Name });

                }

            }
        }


        private void attcont(string texto )
        {

            this.txtTexto.Text += texto + "\n";

        }
        private void attcont1(string texto)
        {

            this.txtTexto1.Text += texto + "\n";

        }
        private void attcont2(string texto)
        {

            this.txtTexto2.Text += texto + "\n";

        }







        private void txtTexto_TextChanged_1(object sender, EventArgs e)
        {
            txtTexto.SelectionStart = txtTexto.Text.Length;
            txtTexto.ScrollToCaret();
        }

        private void txtTexto1_TextChanged(object sender, EventArgs e)
        {
            txtTexto1.SelectionStart = txtTexto1.Text.Length;
            txtTexto1.ScrollToCaret();
        }

        private void txtTexto2_TextChanged_1(object sender, EventArgs e)
        {
            txtTexto2.SelectionStart = txtTexto2.Text.Length;
            txtTexto2.ScrollToCaret();
        }

        private void label3_Click(object sender, EventArgs e)
        {

        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void label4_Click(object sender, EventArgs e)
        {

        }

        private void label4_Click_1(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
    }

}