electricity bill

#include<stdio.h>
void main()
{
    float a,cno,bill;
    char nm[50],add[50],ch;
    FILE *f1,*f2;
    f1=fopen("in1.txt","r");
    if(f1==NULL)
        printf("file cannot be opened\n");
    f2=fopen("out1.txt","w");
    if(f2==NULL)
        printf("file cannot be opened\n");
    do
    {
        fscanf(f1,"%s %f %s %f",nm,&cno,add,&a);
        if(a>200)
            bill=300+((a-200)*3);
        else
            if(a>100)
                bill=100+((a-100)*2);
            else
                bill=a;
            fprintf(f2,"%s\t%.2f\t%s\t%.2f\tRs%.2f\n",nm,cno,add,a,bill);
    }while((ch=getc(f1))!=EOF);
    fclose(f1);
    fclose(f2);
}