C program for calculate electric bill

Calculate electric bill C program

#include<stdio.h>
void PrintBill(float units,float a[5],float extraCharge,char firstName[100],char lastName[100],int range[8]);
main(){
 int i,choice;
 float units,extraCharge,totalBill,sum=0.0;
 char firstName[100],lastName[100];
 printf("Enter\n1.To Calculate electricity of your own custom values\n2.To use Predefined values\n");
 scanf("%d",&choice);
 switch(choice)
 {
  case 1:
  {
   int k=0;
   float a[5];
   int range[8]={1,50,51,100,101,200,201,300};
   printf("Enter First Name\n");
   fflush(stdin);
   gets(firstName);

   printf("Enter Last Name\n");
   fflush(stdin);
   gets(lastName);
   for(i=0;i<5;i++)
   {
    if(k<7)
        printf("Enter Cost/Unit for %d - %d units\n",range[k],range[k+1]);
    else
     printf("Enter Cost/Unit for >300 units\n");

    scanf("%f",&a[i]);
    k+=2;
   }
   printf("Enter Extra Charge\n");
   scanf("%f",&extraCharge);

   printf("Enter Total Number of Units used/consumed\n");
   scanf("%f",&units);
      PrintBill(units,a,extraCharge,firstName,lastName,range);
   break;
  }
  case 2:
  {
   int k=0;
   int range[8]={1,50,51,100,101,200,201,300};
   float a[5]={1.2,3,3.3,4.1,5.2};
   extraCharge=3.5;
   printf("Enter First Name\n");
   fflush(stdin);
   gets(firstName);

   printf("Enter Last Name\n");
   fflush(stdin);
   gets(lastName);
   printf("Enter Total Number of Units used/consumed\n");
   scanf("%f",&units);
   PrintBill(units,a,extraCharge,firstName,lastName,range);
   break;
  }
  default:
  {
   printf("Enter Valid Choice\n");
  }
 }

}

void PrintBill(float units,float a[5],float extraCharge,char firstName[100],char lastName[100],int range[8]){
 float sum=0.0,totalBill;
 int k,i;
  if(units>=1 && units<=50)
   {
    sum=units*a[0];
   }
   else if(units>=51 && units<=100)
   {
    sum=(50*a[0])+((units-50)*a[1]);
    printf("sum (50*a[0])+((units-50)*a[1])= %f",(50*a[0]));
   }
   else if(units>=101 && units<=200)
   {
    sum=(50*a[0])+(50*a[1])+((units-100)*a[2]);
   }
   else if(units>=201 && units<=300)
   {
    sum=(50*a[0])+(50*a[1])+(100*a[2])+((units-200)*a[3]);
   }
   else
   {
    sum=(50*a[0])+(50*a[1])+(100*a[2])+(100*a[3])+((units-300)*a[4]);
   }
   totalBill=sum+(extraCharge*sum);
   printf("\n\n******************Hi %s %s*********************\n\n******Your Electricity Bill*********\n",firstName,lastName);
   printf("\n       Unit Range         Cost\n");
   k=0;
   for(i=0;i<5;i++)
   {
    if(k<7)
        printf("%9d - %d",range[k],range[k+1]);
    else
     printf("      >300    ");
    if(i!=0 && i!=4)
        printf("%15.2f\n",a[i]);
    else
        printf("%16.2f\n",a[i]);
    k+=2;
   }

   printf("\nSum=%f\n",sum);
   printf("Collecting Extra Charge of %f on total amount of %f\n",extraCharge,sum);
   printf("\nTotal Amount Costed=%f\n",totalBill);
}

Output:

Enter
1.To Calculate electricity of your own custom values
2.To use Predefined values
1
Enter First Name
Mahi
Enter Last Name
G
Enter Cost/Unit for 1 - 50 units
0.4
Enter Cost/Unit for 51 - 100 units
0.56
Enter Cost/Unit for 101 - 200 units
0.9
Enter Cost/Unit for 201 - 300 units
1.2
Enter Cost/Unit for >300 units
3
Enter Extra Charge
0.4
Enter Total Number of Units used/consumed
299


******************Hi Mahi G*********************

******Your Electricity Bill*********

       Unit Range         Cost
        1 - 50            0.40
       51 - 100           0.56
      101 - 200           0.90
      201 - 300           1.20
      >300                3.00

Sum=256.799988
Collecting Extra Charge of 0.400000 on total amount of 256.799988

Total Amount Costed=359.519989
        

Explanation:
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