David designs floor tiles. His latest design is shaped as a regular pentagon. Write a formula for the perimeter of the tile in terms of the length of a side. Evaluate the formula for the side length of 3 inches.
a. P = 5s; 15 inches
b. P = 5 + s; 8 inches
c. P = 5 + s; 9 inches
d. P = 5s; 18 inches