You are given the following class definition:

class Ratio$\{$

private:

int num, den;

public:

Ratio$($int n$,$ int d$)$;

explicit Ratio$($int n$)$;

Ratio$($const Ratio& r$)$;

void operator$=($Ratio& a$)$;

friend ostream& operator$<<($ostream& ostr, Ratio a$)$;

$\}$

Examine the following code. State after each line of the code whether a member

function of the class has been called or not. If yes, state which function was called.

Note that the output of the code is not required, as the function definitions are not

given:

Ratio a$(3,7)$;

Ratio c$(2)$;

cout $<<$ a $<<$ endl;

$\{$Ratio d$=$c;

$\}$ int n $=4$;