Cliff bought a new smartphone for $8,000 last year. Yesterday, due to his carelessness, the phone fell from his table and the screen was broken. He can sell the phone with the broken screen for $500 to a potential buyer or he can first spend $400 to have the screen replaced and then sell the repaired phone for $950. a. Discuss the marginal benefit of replacing the screen. b. Use the marginal analysis to decide whether the screen should be replaced before selling to the potential buyer. C. Suppose due to the pandemic, a lot of mobile phone makers lack parts such as chips to produce the new model of phones which leads to the delayed schedule of its debut. Many mobile phone users then delay the plan of changing their mobile phones and keep using their existing phones for longer time (instead of selling them in the second-hand market). Use a well-labeled supply-and- demand diagram to illustrate its effect on the equilibrium price and equilibrium quantity of the used mobile phone market