Problem: Write a program that reads in a loan amount, an 
annual percentage rate (for example, 7.5 would be 7.5 %), and term in months 
and displays the monthly payment amount for the loan. Calculate this amount 
using function calc_month_pay. 

Develop a case study before you come to lab!

To code  the program,

1.  Write the prototype for function calc_month_pay.

2.  Write the main function.

3.  Write function calc_month_pay.

To calculate the monthly payment use the formulas below in function 
calc_month_pay:

1.  monthly_rate = annual_rate / 1200.0

2.  expm = (1.0 + monthly_rate)

			
3. 		      monthly_rate x expm ^ months x loan
monthly payment =  ----------------------------------------
				(expm ^ months) - 1.0

where ^ means raise to a power. Don't concern yourself about what expm 
means. It is a variable in formula 3. Its value is set by formula 2 
before it is used in formula 3.

*************************************************************************
******  Note:  You must use pow(expm, (double) months) to calculate
        expm ^ months otherwise you get a floating point exception error.
*************************************************************************

4.  Additional assignment due before lab next week.

5.  Change function calc_month pay in the following way:

   Before calculating the monthly rate, 
   if the loan amount is over 100000.00, deduct 0.5% from the annual 
percentage rate. If the loan amount is not over 100000.00 but is over 
50000.00, deduct 0.25% from the annual percentage rate. Function 
calc_month pay should call a new function adjust_rate to do this.

6. Write function adjust_rate.

Extra credit:

Add a function display_table which will display a table that 
looks like the following:

Total payments for a loan of $10000.00, term of 10 years, 
and interest rate of 6.0 %

Year 		Amount paid to date		
1			1500.00
2			3000.00
3			4500.00
...

When you call this function, you will have to pass it the 
monthly payment and the number of months of the loan.

The body of this function should look something like the 
following. Complete the function heading and body.

void display(...)
{
   double annual_payment;   //annual payment
   int num_years;               //years of loan

   //Calculate annual_payment given month_payment;
   annual_payment = ...
   num_years = months / 12;

   total_payment_so_far = 0.0;
   //Display the total amount paid at the end of each year
   for (year = 1;  year <= num_years;  year++)	
   {
     //Add annual_payment to total_payment_so_far
     total_payment_so_far = 
                total_payment_so_far + annual_payment;

     printf("%d%15.2f\n", year, annual_payment);
   }
}