To solve this, we need to find the length of side FE using the Pythagorean Theorem, a^2 + b^2 = c^2. Sides FD and DE are both 3 units long.
3^2 + 3^2 = c^2
9 + 9 = c^2
18 = c^2
sqrt18 = sqrtc^2
4.2 ≈ c
Now, we will add all three sides. 4.2 + 3 + 3 = 10.2. The correct answer is C, 10.2 units.