A function f is continuous on (0,6) and satisfies the following.
• f is increasing on (0,3) and decreasing on (3,6).
• f has a local maximum at x=3.
Let F(x)=∫1xf(t)dt for 1≤x≤6. Which statement about the concavity of F is true?
a) F is concave up on (0,3) and concave up on (3,6).
b) F is concave down on (0,3) and concave up on (3,6).
c) F is concave up on (0,3) and concave down on (3,6).
d) F is concave down on both (0,3) and (3,6).