结构体+点餐的总价格怎么算的问题？

Question

题目：开心区餐厅是广州市的一家餐厅。餐厅主要供应一般的食物和饮料，如酒、餐、蔬菜、海鲜等（如表1所示）。为了成为一家高级国际餐厅，餐厅要求每桌的最后帐单必须是100%正确的。因此，餐厅决定开发一个由收银员选择食物或饮料，然后计算和输出最终客户的帐单的系统。经理现在要求您完成这项工作，他希望系统能由收银员选择食物或饮料，然后程序将计算并输出最终帐单。
问题：paymoney的价格怎么算？不会。
情况：目前大体上程序可以运行，就是价格运算有问题。

#include<iostream>
#include<stdio.h>
struct food
{
    int ID;
    char Name[50];
    char typr[20];
    float price;
    int number;    //点菜时考虑点几分 
};
void payMoney()
{
    int n,m,total;
    
    
    total=n+m;
    printf("food %dRMB\n",n);
    printf("Drink %dRMB\n",m);
    printf("Total:%dRMB\n",total);
}
void ShowMainMenu()
{
    printf("\n*********************************\n");
    printf("*            1.点菜               *\n");
    printf("*            2.结账               *\n");
    printf("*            3.增加新菜品         *\n");
    printf("*            4.退出               *\n");
    printf("\n*********************************\n");
}
int ShowMenu()
{   
    food fd[8]=
    {{1,"Curry beef with rice","food",40,0},
    {2,"Sushi set meal","food",65,0},
    {3,"YangZhou fire rice","food",45,0},
    {4,"Sirloin Steak with Spaghetti","food",72,0},
    {5,"Chicken vegetable roll","food",42,0},
    {6,"Soft drink\t" ,"drink",10,0},
    {7,"Red wine\t" ,"drink",10,0},
    {8,"Beer\t" ,"drink",10,0},} ;
    printf("\n#########################################\n");
    for(int i=0;i<8;i++)
    {
        printf("#%d.%s\t %10.2f$\t #\n",fd[i].ID,fd[i].Name,fd[i].price);
    }    
int sel=0;
while(1)
{
 scanf("%d",&sel);
 switch(sel)
 {
  case 0:
   ShowMainMenu();
       return 1;
  default:
   printf("已点好了%d号菜了,如果点完菜，请按'0'退出\n",sel); 
       break;  
 }
} 
}
void SelectMainMenu()
{
        char c;
    while(1)
    {
        scanf("%c",&c);
        switch(c)
        {
            case '1':
                ShowMenu();
                break;
            case '2':
                payMoney();
                break;
            case '4':
                return;     
        }
    }    
}
#include<stdio.h>
#include"jiegou.h"
int main()
{
    printf("*****************开心区餐厅*******************\n");
    printf("*****************欢迎您点菜*******************\n");
    ShowMainMenu();
    SelectMainMenu();
    payMoney();
    return 0;
}