a. Design a PhoneCall class that holds a phone number to which a call is placed, the length of the call in minutes, and the rate charged per minute. Overload extraction and insertion operations for the class.
b. Overload the == operator to compare two PhoneCalls. Consider one PhoneCall to be equal to another if both calls are placed to the same number.
c. Create a main() function that allows you to enter 10 PhoneCalls into an array. If a PhoneCall is already been placed to a number, do not allow a second PhoneCall to the same number