Consider the system shown in the figure $($Figure $1).$ Block A has weight wA and block B has weight w$.$ Once block B is set into downward motion, it descends at a constant speed. Assume that the mass and friction of the pulley are negligible.A cat, also of weight wA$,$ falls asleep on top of block A$.$ If block B is now set into downward motion, what is the magnitude of its acceleration?Express your answer in terms of some or all of the variables wA$,$ wB$,$ and g $($the acceleration due to gravity$).$