Q1) A little ambiguous, but assuming the situation is you are depositing $1429 into an account every month and earning % on that account, then I would solve it as follows:

Monthly rate

Future value of your annuity

To find the amount of interest paid, simply subtract all the deposits of $1429 and see what you have left over.

Question two is exactly the same, accept your regular payment is now 402, your rate is 0.03/12 and the number of payments is 6*12.