Two blocks A and B of masses 3m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively : 

\(\frac{g}{3}\), g

Before the string is cut 

kx = T + 3 mg 

t = mg

kx = 4 mg

After the string is cut, T = 0

a = \(\frac{kx - 3 mg}{3 m}\)

a = \(\frac{g}{3}\)