What is the work done by a coolie on the bricks when he is carrying bricks on a slope if the mass of the bricks are 10kg and the mass of the coolie is 50kg and height is 10m ,Also find the total work done by him

According to piaget’s stages of cognitive development, the child does not differentiate between self and other objects. the child repeats rewarding activities, discovers new ways to get what he or she wants, and may have imaginary friends. which period is described?