Add the following member function to the ADT class DigitalTime

defined in Displays 12.1 and 12.2:

This function computes the time interval between two values of type

DigitalTime. One of the values of type DigitalTime is the object that

calls the member function interval_since, and the other value of type

void DigitalTime::interval_since(const DigitalTime& a_previous_time,

int& hours_in_interval, int& minutes_in_interval) const

DigitalTime is given as the first argument. For example, consider the

following code:

DigitalTime current(5, 45), previous(2, 30);

int hours, minutes;

current.interval_since(previous, hours, minutes);

cout << "The time interval between " << previous

<< " and " << current << endl

<< "is " << hours << " hours and "

<< minutes << " minutes.\n";

In a program that uses your revised version of the DigitalTime ADT, this

code should produce the following output:

The time interval between 2:30 and 5:45

is 3 hours and 15 minutes.

Allow the time given by the first argument to be later in the day than the

time of the calling object. In this case, the time given as the first argument

is assumed to be on the previous day. You should also write a program to

test this revised ADT class.