error: incompatible type for argument 1 of `total'

#include <stdio.h>
float total(float, int);

typedef struct BOOK
{
	int serial;
	char title[30];
	char author[30];
	float price[30];
	int quantity;
}BOOK;

int main()
{
	BOOK a[2];
	int x;
	float sum;
	for(x=0;x<2;x++)
	{
           printf("Please Enter Your Book Serial Number :\n");
           scanf("%d", &a[x].serial);
           printf("Please Enter Your Book Title :\n");
   	   scanf("%s", &a[x].title);
           printf("Please Enter Your Book Author :\n");
   	   scanf("%s", &a[x].author);
           printf("Please Enter Your Book Price :\n");
           scanf("%f", &a[x].price);
           printf("Please Enter Book Quantity :\n");
           scanf("%d", &a[x].quantity);
           sum = total(a[x].price, a[x].quantity);
	}
	
    printf("Your Total Is : %.2f\n",sum);
    return 0;
}

float total(float z,int y)
{
	return z*y;
}