Tim manufactures chairs, and each requires 4 feet of lumber. 1,500 and 1,700 chairs will be built

Question:

Tim manufactures chairs, and each requires 4 feet of lumber. 1,500 and 1,700 chairs will be built in April and May, respectively. Tim keeps lumber on hand at 40% of the next month's production needs. How many feet should Tim buy in April?
A) 6,300
B) 6,320
C) 8,720
D) 5,980