FIFO PROBLEM

In March, 2013, M/S RB purchased 5 boxes  at a  cost of $5,000. In June, 2013, it purchased 3 boxes  a total cost of $6,000. In October, 2013, it bought 2 boxes at a cost of $1,000. It sold 6 boxes in December, 2013. What is  ending inventory as per FIFO ?

a. $12,000 .

b. $5,000 .

c. $7,000 .

d. $5,400 .