Write a function declaration and a function definition for a function that
takes one argument of type int and one argument of type double, and that returns a value of type double that is the average of the two arguments.
The function declaration is:
double ave(int n1, double n2);
//Returns the average of n1 and n2.
The function definition is:
double ave(int n1, double n2)
{
return ((n1 + n2)/2.0);
}