Two masses, M>m, are connected by a light string hanging over a pulley of negligible mass. When the masses are released from rest, the magnitude of the acceleration of the masses is:
a. ((M+m)/(M-m))g
b. ((M-m)/(M+m))g
c. ((M)/(M+m))g
d. ((m)/(M+m))g
e. ((M-m)/(M))g