RunTimer Error 205 - Floating Point Overflow

I had an assignment to:
1. write a program that prompts the user for the amount of laon, length of
loan in years, low interest rate and a high interest rate.
2. Print out monthly payment for teh different interest rates from low to
high, incremented by 0.25%
3. Make use of power calculations
4. Use a repeat loop to solve the problem.

I've encountered this error in the following program:
RunTimer Error 205
which the help file says is a Floating Point Overflow, where the number is
to big.
I've figured out the line with the problem, but I can't figure out how to
fix it.
It only occurs with higher number of years (30 did it).  I can get it to
work fine with smaller time periods.

Any help would be appreciated.

program Loan;

uses WinCRT;  {just change this line to run it in DOS Turbo Pascal or
Macintosh Think Pascal}

var
 p,k,n,c,a,y,t,h,l : real;
{principal, monthly rate, number of payments, (1 + k)^n}
{monthly payment, years, temp rate, high rate, and low rate,}

function power(B,E:real):real;

begin {power}
 power:=exp(E*ln(B));  {THIS IS THE LINE WITH THE ERROR}
end; {power}
begin {main}
 writeln('Welcome to the Financial Loan Analyzer');
 writeln;
 writeln('In order to calculate your monthly payment options,');
 writeln('I''ll need three pieces of information.');
 writeln('Please enter each one when prompted');
 writeln;
 write('Amount of Loan (Principal) : ');
 readln(p);
 writeln;
 write('Number of Years before paying off Loan : ');
 readln(y);
 writeln;
 write('Low Interest Rate of Loan : ');
 readln(l);
 writeln;
 write('High Interest Rate of Loan : ');
 readln(h);
 writeln;
 n := y * 12; {assign # of payments to years * 12}
 t := l;
 repeat
  k := t / 12; {assign monthly rate to yearly / 12}
  c := power(1+k,n); {do what the book tells me to do}
  a := (p * k * c) / (c - 1); {assign a the monthly payment}
  writeln('Interest Rate':20,'Monthly Payment':20);
  writeln(t:20:2,a:20);
  t:= t+0.25;
 until t >= h;
end. {main}

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~AKBis...@aol.com
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