The figure below shows a block with a mass of $m=4\mathrm{.}40kg$ that starts from rest at point A and slides on a track with negligible friction. Point $A$ is at a height of $h_a=6\mathrm{.}90m.$

$($a$)$ What is the block's speed at point B $($in $\frac{m}{s})?$

$\frac{m}{s}$

What is the block's speed at point $C($in $\frac{m}{s})?$

$\frac{m}{s}$

$($b$)$ What is the net work $($in J$)$ done by the gravitational force on the block as it moves from point A to point C$?$