以下程序运行结果不对，但是我没检查出来

有以下程序，用switch语句，为了打折促销，1000元以上打9.5折，2000元以上打9折，3000元以上打8.5折，5000元以上打8折，程序如下#include <iostream>
using namespace std;
int main()
{
    int c;
    float total_payment, discount_rate, real_payment;
    cout << "plase input total_payment for goods:";
    cin >> total_payment ;
    c = total_payment / 1000;
    switch(c)
    {
        case 0: discount_rate=1; break;
        case 1: discount_rate=0.95; break;
        case 3: discount_rate=0.9; break;
        case 4:
        case 5: discount_rate=0.85; break;
        difault : discount_rate=0.8; break;
    }
    real_payment = discount_rate * total_payment;
    cout << "the real payment is:" << real_payment << endl;
    return 0;
}
可是当输入8000元时，结果不对啊，是哪里出错了？