i hope i can have explanation about how to find the answers. Thank you so much.

Question 3 In a bond portfolio, 30% of the holding is of 5-year duration, 20% is of 2-year duration, and 50% is of 1-year duration. What is the duration of this portfolio? (10 marks) Question 4 The following yield curve is observed of the U.S. Treasury securities on 1 October 2019: Maturity (year) 2 3 Yield Rate 1.73% 1.56% 1.51% Suppose the pure expectation theory is correct. Forecast the expected one-year yield rate in second and the third year accordingly. (10 marks)