The estimated overhead for the cost pool, machine set-ups, is 5180 000. The machines in the pool produce three products: X (300 set- ups); Y (200 set-ups) and Z (500 set-ups). If 20 000 units of product X are produced, the amount of machine set-up costs that will be assigned to each unit of X is: Select one: a. $4.50 b. $9.00 O c. $2.70 d. $1.80