The base is from 2 to 7, which is 5 units long.
The height is from 1 to 8, which is 7 units tall.
Using the Pythagorean theorem we can calculate the hypotenuse:
Hypotenuse = √5^2 +7^2=
√25 +49=
√74=
8.6
Perimeter = 5 + 7 + 8.6 = 20.6
The answer is C.