Well if Block A is on top of Block B, then the total mass is the sum of Block A and Block B. Therefore the total mass is 16kg. Since the blocks are not moving, the force of gravity is equal to the normal force.
The top of the trajectory is the point where it changes from rising to falling. At that exact instant, its vertical speed is zero.
Oh easy it was the archduke franz
V: there would be no seasons and humanity would suffer