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