A) From rest and before performing the described exercise, the entire weight of the desk is supported by the floor. This support force (normal force) exerted by the floor will be equivalent to the force equivalent to the weight of the desk. From the moment the desk starts to be lifted, said support force will decrease and the weight of the desk supported by the floor will be less.
B) As the desk is lifted, the support force of the two guests will increase, this occurs because the force is transferred to the support of both, but the support force of the floor on the two people will increase.
