Problem help

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define DISCOUNT_10 10
#define DISCOUNT_12 12
#define NETTAX 5

int main(void)
{
  char customer;
  int purchase; 
  double discount2;
  double discounttl;
  double salestax;
  double purchasettl;
  
    printf("Is customer a teacher (Y/N) ?>");
    scanf("%c", &customer);
    printf("\nEnter total purchases:>");
    scanf ("%d", &purchase);
    
    if (customer == 'Y' && purchase > 100) {
       discount2 = purchase * 0.12;
       discounttl = purchase * 0.88;
       salestax = discounttl * 0.05;
       purchasettl = discounttl * 1.05;
                   printf("\nTotal purchases        $%6.2lf\n", double(purchase));
                   printf("Teacher's discount(%d%%)  %6.2f\n", DISCOUNT_12, discount2);
                   printf("Discounted total          %6.2f\n", discounttl);
                   printf("Sales tax(%d%%)           %6.2f\n", NETTAX, salestax);
                   printf("Total                     %6.2f\n", purchasettl); 
                   }     
                   
    if (customer == 'Y' && purchase < 100)
                   {
                  discount2 = purchase * 0.10;
                  discounttl = purchase * 0.90;
                  purchasettl = discounttl * 1.05;
                  }
                  printf("\nTotal purchases $%6.2lf\n", purchase);
       printf("Teacher's discount (%d%%)  %6.2lf\n", DISCOUNT_10, discount2);
       printf("Discounted total %6.2lf\n", discounttl);
       printf("Sales tax(5%) %6.2lf\n", NETTAX, salestax);
       printf("Total %6.2lf\n", purchasettl);
        
    if (customer == 'N') {
       purchasettl = purchase * 1.05;
       printf("\nTotal purchases $%.2f\n", purchase);
       printf("Sales tax(%d%%) %.2f\n", NETTAX, salestax);
       printf("Total %.2f", purchasettl);
       }
       
       system ("pause");
       return (0);
       }