Spawn manager from Top/Left/Right of Screen

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SpawnManager : MonoBehaviour
{
    //array for the prefab animals
    public GameObject[] animalPrefabs;

    private float spawnRangeX = 20;
    private float spawnPosZ = 30;

    public float sideSpawnMinZ;
    public float sideSpawnMaxZ;
    public float sideSpawnX;

    private float spawnDelay = 2;
    private float spawnInterval = 5f;
    void Start()
    {
        InvokeRepeating("SpawnRandomAnimal", spawnDelay, spawnInterval);
        InvokeRepeating("SpawnLeftAnimal", spawnDelay, spawnInterval);
        InvokeRepeating("SpawnRightAnimal", spawnDelay, spawnInterval);

    }

    void Update()
    {
        //pressing S spawns an animal
       // if (Input.GetKeyDown(KeyCode.S))
        {
      //     SpawnRandomAnimal();
        }
    }
    void SpawnRandomAnimal()
    {
        //randomises the position of spawn on X axis
        Vector3 spawnPos = new Vector3(Random.Range(-spawnRangeX, spawnRangeX), 0, spawnPosZ);
        //randomises the animal spawned
        int animalIndex = Random.Range(0, animalPrefabs.Length);
        //spawns animal at position
        Instantiate(animalPrefabs[animalIndex], spawnPos, animalPrefabs[animalIndex].transform.rotation);
    }

    void SpawnLeftAnimal ()
    {
    int animalIndex = Random.Range(0, animalPrefabs.Length);
        Vector3 spawnPos = new Vector3 (-sideSpawnX, 0, Random.Range(sideSpawnMinZ, sideSpawnMaxZ));
        Vector3 rotation = new Vector3 (0, 90, 0);
        Instantiate(animalPrefabs[animalIndex], spawnPos, Quaternion.Euler(rotation));
    }

    void SpawnRightAnimal()
    {
        int animalIndex = Random.Range(0, animalPrefabs.Length);
        Vector3 spawnPos = new Vector3(sideSpawnX, 0, Random.Range(sideSpawnMinZ, sideSpawnMaxZ));
        Vector3 rotation = new Vector3(0, -90, 0);

        Instantiate(animalPrefabs[animalIndex], spawnPos, Quaternion.Euler(rotation));
    }
}