Compound interest help?

yu decided to borrow $200000 to buy investment property.
bank agreed to lend the money over a period of 25 years at 6% per annum by monthly installments
1. calculate the repayment yu must make on the loan
A = 200000 * 0.005
------------------------
1 鈥?(1.005)25*12
= $1288.60
2. at the end of the fifth year you is repaying the loan . How much interest he would save if he repaid at this point.
No. of remaining instalment = 20 * 12 =240
Payout figure = 1288.60 * 1-(1.005)-240
----------------
0.005
=179863.78
Savings=1288.60 * 240 鈥?179863.78
= $129400.22
3. at the end of tenth year there is a rise in interest to 9%
calculate the new repayment amount.
Terms of loan = (25-10) = 15*12 =180
I = 9%/12
= 179863.78 * 0.0075
------------------------
1- 1.0075-180
= $1824.29
4. if he wants to continue with original repayments how many additional years are required to repay the loan.
Additional payment for 15 yrs = (1824.29-1288.60)*120

This is not a "investing" question, but rather a homework question.

Your question and presentation is sloppy and you pay no attention to detail -- that's why you're in trouble

You say it's a 6% loan, then give us 1-(1.005)*25*12

You don't even give us units, like 25 yrs * 12 mo. It's difficult to distinguish years from dollars from percentage. Too much work; clean it up.

the answer is 42