Coin $1$ slides across a horizontal surface with speed $v$ and collides with identical Coin $2$ that is initially at rest. Immediately after the collision, Coin $2$ has speed $\frac{3v}{4}.$ Which of the following correctly describes the speed $v_1$ of Coin $1$ immediately after the collision and how the kinetic energy of the two$-$coin system changes, if at all, during the collision? Frictional forces are negligible.

Speed of Coin $1$

Kinetic Energy

A

$v_1=0$

Remains constant

B

$v_1=0$

Decreases

C

$v_1=\frac{v}{4}$

Remains constant

D

$v_1=\frac{v}{4}$

Decreases