7. On an investment company there are two alternatives to execute the civil work for a high tension transmission line. The first one is by 15 hand labor with an annual wage bill of 15000 $ and with other expenses the total cost will be 20000 $ per year and the project duration expected to be 6 years in this case. The second alternative is to buy a machine for 22000 S and reduce the labor force to 6 men including the driver and the cost for labors are 9000 $ per year. The maintenance of the machine is estimated to be 800 $ and 1000 $ after 2 and 4 years respectively and it will have a savage value of 800 S. Which scheme is best economically if the interest rate is 20%