Few tasks in life are more complex than selecting long distance service. Numerous long distance service providers exists, both nationally and locally, and each of those in turn offers numerous calling plans to choose from. This can be viewed as positive for the consumer, who is able to choose plans tailored to personal calling patterns, or negative due to the overall complexity of the system. In fact, Scott Adams described the long distance service industry as a "confusopoly", where a group of companies with similar products resort to confusing the customer as opposed to competing directly on price (The Dilbert Future, Scott Adams, Harper-Collins Publishers, Inc., 1997).

The following long distance plans were taken from the Sprint Web site www.sprint.com on 9/29/01, and don't even exhaust the selection of plans offered. Note: the selection of Sprint over other long distance service providers such as AT&T and MCI is purely random. It is not intended as an endorsement or criticism of Sprint or its policies.

You are to write a C++ program that allows the customer to determine which of these plans best meets their needs, based on their calling patterns. First, the program should ask whether the user is interested in a specific plan or in comparing the costs under all plans. In the case of a specific plan, the program should prompt the user to determine which of the six plans is of interest, and also the number of daytime and night minutes that they foresee using each month. In the case of the second option, comparing all plans, the costs under all of the six plans should be computed and displayed (entering the daytime and night minutes only once, of course).

The following sample executions demonstrate the intended behavior of the program (with user input displayed in bold):

Requirement 1: At the bare minimum, your program should define functions for each of the different calling plans, with parameters corresponding to the values that vary for that plan, either total minutes (for the Anytime plans) or daytime and night minutes (for the Night plans). Other function definitions may be called for as well.

Requirement 2: Your program should produce meaningful output even if the customer enters invalid responses at the prompts. For example, if the customer enters a 3 at the first prompt (where only two options are presented), the program should display an error message and exit gracefully. Likewise if the customer enters an invalid plan number at the second prompt. In the case of an invalid response, the user should NOT be prompted for daytime and night minutes.

Requirement 3: As you start to write more complex programs, readability becomes an even higher priority. This and all subsequent programs should meet the following style guidelines:

• There should be a comment block at the top of the file containing the file name, author name, date, and a short description of the program.
• Well-defined computations of non-trivial length merit their own function definitions, as do tasks that are repeated throughout the program.
• Every function should have comments that describe its behavior, as well as any assumptions about the parameters (see examples from the lectures).
• Constants should be declared at the top of the program for values that remain constant throughout execution, but could conceivably change from execution to execution.
• Function prototypes should be placed above main, with all function definitions appearing below main.
• Blank lines should be used to separate logical tasks performed within the code (a.k.a. "paragraphing" the code).
• Consistent indentation should make the structure of the code clear.