Two persons P and Q are standing 54m apart on a long horizontal belt moving with a speed of $4ms^{-1}$ in the direction from P to Q.Person P rolls a round stone towards person Q with speed of $9ms^{-1}$ with respect to the belt.The velocity of stone with respect to an observer on a stationary platform is

Question

$\begin{array}{1 1}13ms^{-1}\text{ in the direction to motion of the belt}\\13ms^{-1}\text{ opposite to the direction of motion of the belt}\\5ms^{-1}\text{ in the direction to motion of the belt}\\5ms^{-1}\text{ opposite to the direction of motion of the belt}\end{array} $