A firm purchased 25 units of materials with a unit price of $2.00 on May 5. On may 15, the firm purchased 25 units with a unit price of $2.10. If the firm uses FIFO method of inventory pricing, the total cost of 30 units issued on May 20 would be: a)$62.50 b)$60.00 c)$63.00 d)$60.50