4. A manufacturer needs to replace a machine. It was purchased 3 years ago at $60,000. Its current market value is $30,000. This market value is expected to decline by 30% per period (from the previous period) until it reaches zero at the end of period 8. The estimated operating and repair cost for the next period is $18,000 and this is expected to grow at a rate of 10% per period. The old model is no longer made, and a new model that can replace this machine is sold at $90,000. After one period the market value of this new model will be $70,000 and this value is expected to decrease by 25% per period until the expected end of service after 15 periods. The first period operating cost is expected to be $10,000 increasing by 10% per year. Applying an interest rate of 15%, answer the questions below. a. What is the economic service life of the current machine? b. What is the lowest period equivalent cost for keeping the current machine in operation for the economic service life? c. What is the economic service life of the new machine? d. What is the lowest period equivalent cost for keeping the new replacement machine in operation for its economic service life? e. Based on your analysis, what should be your strategy regarding replacement? Why? (Please support your decision with numbers.)