A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m. If a force P is applied at the free end of the rope, the force exerted by the rope on the block will be

Question

$$(a)\;P \quad (b)\;\frac{Pm}{M+m} \quad (c)\;\frac{mp}{M+m} \quad(d)\;\frac{MP}{M+m}$$