Calculating the Perimeter of a Rectangular Pond

Tom is building a rectangular fish pond in his backyard. The pond will be 10 feet long and 4 feet wide. He wants to find out how much fencing he needs to go around the pond. To find the perimeter of the pond, he can use the formula:

$P = 2(l + w)$

where $l$ is the length and $w$ is the width. What is the total length of fencing required?