Hello Tutor, please I need help with those question to prepare for my exam

1) Joan borrowed $3000 today with the understanding that she would repay the loan in two payments: $1600 in one year and a second payment of $1700. If interest is 8% compounded quarterly, when should the second payment be made?

2) A contract requires payments of $4000 today, $5000 in three years, and $6000 in five years. When can the contract be fulfilled by a single payment equal to the sum of the required payments if money is worth 9% p.a. compounded monthly?

3) Graham purchased a business by agreeing to make three payments of $12 000 each in one year, two years, and four years. Because of cash flow difficulties in the first year, he renegotiated the payment schedule so that he would pay $16 000 in 18 months, $10 000 in 30 months, and a third payment of $10 000. In how many years should he make the third payment if interest is 7.2% compounded semi-annually?

your help is really appreciated. Thank you