The question states that masses A and B are in a lift of mass 250kg. The lift is in constant acceleration upwards and the lift exerts a reaction force of magnitude 678N and 452N on masses A and B respectively. It also states the tension on lift is 3955N.
I looked at the solution bank and it is taking the reactions forces to be the weight of the masses and solves the problem by applying n2l on the lift only. I was taught that the reaction force is different to the weight of the object when in acceleration so the force exerted on the lift is equal to the weight of the masses of the 2 masses.