Please show step by step how to find this including PV of payments calculations and time weighted? ive seen this question on chegg but cannot figure it out.

Also why is the coupon bond 9% in all examples?

4. A bank has two 3-year commercial loans with a present value of $70 million. The first is a $30 million loan that requires a single payment of $37.8 million in three years, with no other payments till then. The second loan is for $40 million. It requires an annual interest payment of $3.6 million. The principal of $40 million is due in three years. a. What is the duration of the bank's commercial loan portfolio? b. What will happen to the value of its portfolio if the general level of interest rates increases from 8% to 8.5%