单选题 Given the following information and assuming beginning inventory was zero what is the gross profit at the end of the period using the FIFO, LIFO, and average cost methods?

Purchases	Sales
20 units at $ 50	15 units at $ 60
35 units at $ 40	35 units at $ 45
85 units at $ 30	85 units at $ 35

FIFO LIFO Cost Average ①A. $ 650 $ 750 $ 990
②B. $ 650 $ 750 $ 677
③C. $ 677 $ 650 $ 677
A．① B．② C．③