Calculating the Perimeter of a Rectangular Swimming Pool

Sarah has a rectangular swimming pool in her backyard. The length of the pool is 9 feet and the width is 4 feet. Sarah wants to place a decorative tile border around the pool. To find out how many feet of tile she will need, we need to calculate the perimeter of the pool.

The formula for the perimeter of a rectangle is given by:

$$P = 2(l + w)$$

where $$l$$ is the length and $$w$$ is the width.

What is the total perimeter of Sarah's swimming pool?