Jenny wants to replace the wooden floor at her gym. The floor is in the shape of a rectangle. Its length is 40 feet and its width is 30 feet. Suppose wood flooring costs $12 for each square foot. How much will the wood flooring cost for the floor?

The area of the rectangle is 40 x 30 = <<40*30=1200>>1200 square feet.

So, Jenny will need to spend 1200 x $12 = $<<1200*12=14400>>14400 for the wood flooring. Answer: \boxed{14400}.