Math: What is the area

What is the area of a regular octagon with an apothem of 20.8 cm and a side length of 17.2 cm?

A)1987.29
B)1654.23
C)1225.01
D)1431.04

The area of a regular polygon is (1/2)nsa, where n is the number of sides, s is the length of each side, and a is the apothem.
An octagon has 8 sides:

So A = (1/2)(8)(17.2)(20.8)

A= 1431.04

I hope this helps!