How can i call grade variable in function sum

Question

class result{
int grade;
public:
math(){grade= 90;}
bio(){grade=95;}
sum(){grade of math plus grade of bio }
what is the way to sum grades, please??

Answer 1

int sum(int a, int b)
{grade=a;
grade=b;
return(sum of grade );}

Answer 2

int bio()
{grade=90;
return grade;}
int math()
{grade=95;
return grade;}
int sum()
{int s=bio()+math();
return s;}

Answer 3

The sum should have operations of math and bio its parameters.