The Range of the Function F (X) = $\sqrt { 20 + 8 x - x ^ { 2 } }$

Multiple Choice

The range of the function f (x) = $\sqrt { 20 + 8 x - x ^ { 2 } }$ is a closed interval [a; b]. Find its length b - a.

A) 1
B) 2
C) 3
D) 4
E) 5
F) 6
G) 7
H) 9