An engineer must choose between two materials for an underground storage tank. A steel tank costs $206,000 and is expected to last 15 years. A fibreglass tank costs $323,000 and is expected to last 30 years. Neither tank has a salvage value at the end of its useful life. Determine the MARR below which the FRP tank is preferred. Express your answer in % (not a decimal) to the nearest 0.1%.
The engineer of problem 4 now wants to consider an aluminium tank as well as the steel and fibreglass tank. The steel tank costs $225,000 and is expected to last 15 years. The aluminium tank is expected to last 25 years. The fibreglass tank costs $288,000 and is expected to last 30 years. None of the tanks has a salvage value at the end of its useful life. At a MARR of 6%, determine the highest cost for the aluminium tank for which it will be the preferred option. Express your answer in $ to the nearest $1,000.