As mechanics question

A ball, P, of mass 0.4 kg rests on a rough horizontal table and is attached to one end of a thin rope. The rope passes over a pulley which is fixed at the edge of the table. The other end of the rope is attached to another ball, Q, of mass M kg which hangs freely below the pulley, as shown in Figure 1.
The system is released from rest with the rope taut and with Q at a height of 2 m above the ground and Q moves downwards with acceleration 2.5 m s–2. In the subsequent motion P does not reach the pulley before Q reaches the ground.
The balls are modelled as particles, the rope as a light and inextensible string and the pulley as being small and smooth. The total resistance to the motion of P is modelled as having constant magnitude 1.5 N. The acceleration due to gravity is modelled as being 10 m s–2.
Using this model, find, to 2 significant figures,
(a) (i) the tension in the rope,
(ii) the value of M,
(b) the time, after release, for Q to hit the ground.
(c) State one limitation of the model which will affect the accuracy of your answer to part (a).
Does anyone know how to do this?