Let $F(a)$ be the area between the $x$-axis and the graph of $y = x^2 \sin(x/2)$ between $x=0$ and $x=a$, for $a>0$ (consider the area to be negative if the graph lies below the axis).

A. Find a formula for $F(a)$:
$F(a) =$

B. Is $F(a)$ increasing or decreasing for $0<a<2$?

A. decreasing
B. increasing

C. Is $F(a)$ concave up or concave down for $0<a<2$?

A. concave down
B. concave up