Program for calculating Simple Interest using the concept of Default Arguments

//Program for Interest calculation using the concept of default arguments
#include<iostream.h>
#include<conio.h>
void main()
{
float amount, principal;
int time;
float interest(float p, int n, float r=0.15);
cout<<"Program for simple interest calculation"<<endl;
cout<<"Please enter principal amount:";
cin>>principal;
cout<<"Please enter Time: ";
cin>>time;
amount=interest(principal, time);
cout<<"\nThe amount is:"<<amount;
cout<<"\nPress any key to continue...";
getch();
}
float interest(float p, int n,float r)
{
return (p+((p*r*n)/100.0));
}