Slider block $B$ moves to the left with a constant velocity of $50m\frac{m}{s}.$ At $t=0,$ slider block $A$ is moving

to the right with a constant acceleration and a velocity of $100m\frac{m}{s}.$ Knowing that at $t=2s$ slider block

C has moved $40$ mm to the right, determine $($a$)$ the velocity of slider block C at $t=0,($b$)$ the velocity of

portion $D$ of the cable at $t=0,(c)$ the accelerations of A and $C.$