/* Write a function 
that reads a sequence of valid grades (a valid grade is an integer between 0 and 100) 
and prints the number of 
B grades, their sum and returns (a B grade is a grade between 80 and 89) and their average.

In C function can only return ONE value */


#include<stdio.h>
//function prototype

double aveBgrade(); // no parameters
int main(){
	double func_res;
	func_res=aveBgrade();
	if(func_res!=-1)
		printf("ave B grade %f\n",func_res);
	
	return 0;

}

double aveBgrade(){
	int grade, count_B=0, sum_B=0;
	double ave;

	printf("enter a sequence of valid grades\n");	
	scanf("%d",&grade);
	while(grade>=0 && grade<=100){
		if(grade>=80 && grade<=89){
			count_B++;
			sum_B+=grade;
		}
		scanf("%d",&grade);
	}
	if(count_B>0){
		printf("countB = %d, sumB = %d\n",count_B,sum_B);
		ave=(double)(sum_B)/count_B;
		
	}
	else{
		printf("no B grades\n");
		ave=-1.0;
	}
	return ave;
}