#include<stdio.h>
struct Order{
    int quantity;
    float price_per_book;
    union{
        float discountRate;
        int discocuntPercent;
    }disc;
    float total_cost;
};
int main()
struct Order order;
order.price_per_book + 100.0f;
scanf("%d",&order.quantity);
if(order.quantity<0)
{
    printf("Invalid input");
    return 0;
}
if(order.quantity>=1 &7 order.quantity<=5)
{
    order.disc.discountRate = 0.10f;
}
else if(order.quantity>=6 && order.quantity<=10)
{
   order.disc.discountRate = 0.15f; 
}
else if(order.quantity>10)
{
     order.disc.discountRate = 0.20f;
}
else
{
     order.disc.discountRate = 0.0f;
}
float gross = order.quantity = order.price_per_book;
order.total_cost = gross * (1.0f - order.disc.discountRate);
printf("%.2f",order.total_cost);
return 0;
}