Which of the following statement is correct about the program given below?

#include<iostream.h>
const double AptitudeConstant(const int, const int = 0);
int main()
{
    const int c = 2 ;
    cout<< AptitudeConstant(c, 10)<< ' '; 
    cout<< AptitudeConstant(c, 20)<< endl; 
    return 0;
}
const double AptitudeConstant(const int x, const int y)
{
    return( (y + (y * x) * x % y) * 0.2);
}