C++ program sometimes giving wrong answer - c++

Question

I have this program, which should give me the smallest original price of the item based on the input from the user.
There are some conditions, for example, if the quantity of the mask is more than 9 the price will be discounted by 10%, 15% if its more than 30 and 20% if it's more than 50. The result should give the answer Here is my code:
#include <iostream>
#include <iomanip>
using namespace std;
int mprice; //price input
int mquantity; //quantity input
int n; //first input
int fee = 2000; //const fee
float finalprice;
float maskCalc(int price, int quantity) {
float holder = (float)(price - fee) / (float)(quantity);
if (quantity > 0) {
finalprice = holder;
}
//if between 10 and 30
else if (quantity > 9) {
finalprice = holder / 0.9;
}
//between 30 and 49
else if (quantity > 30) {
finalprice = holder / 0.85;
}
//more than 50
else if (quantity > 49) {
finalprice = holder / 0.8;
}
//less than ten
else {
finalprice = holder;
}
return finalprice;
}
int main()
{
cin >> n;
float arr[n];
// Input oruulah loop
for (int i = 0; i < n; i++) {
cin >> mprice >> mquantity;
x = maskCalc(mprice, mquantity);
arr[i] = x;
}
for (int i = 1; i < n; i++) {
if (arr[0] > arr[i]) {
arr[0] = arr[i];
}
}
printf("%.2f", arr[0]);
return 0;
}
I gave the input
3
5000 3
7000 10
3000 1
the answer was 555.56 which is correct, but when I give something like
3
2500 1
7000 10
3000 1
it is giving me 0.00 while I was expecting this to give me 500.00. Any help will be appreciated.

Answer 1

You need to check for the highest quantity first in your if-else switch, otherwise you always fall into the default (<10) case.
//more than 50
if (quantity >= 50) {
finalprice = holder / 0.8;
}
//between 30 and 49
else if (quantity >= 30) {
finalprice = holder / 0.85;
}
//if between 10 and 30
else if (quantity >= 10) {
finalprice = holder / 0.9;
}
//less than ten
else {
finalprice = holder;
}