Write a program to calculate simple interest amount use default value for rate

// write a program to calculate simple interest amount use default value for rate
#include<iostream>
using namespace std;
class interest
{
int period;
float rate;
float principle;
public:
void get()
{
cout<<"Enter principle Amount: ";
cin>>principle;
cout<<"--------------------"<<'\n';
cout<<"Enter no. of period: ";
cin>>period;
cout<<"--------------------"<<'\n';
}
void cal(float rate)
{
float calculation;
calculation=(principle*period*rate)/100;
cout<<"Simple Interest is: "<<calculation<<'\n'<<'\n';
cout<<"--------------------"<<'\n';
}
};
main()
{
interest b;

b.get();
b.cal(3.8);
return 0;
}