A block of mass m is attached to a spring and undergoes simple harmonic motion with amplitude xm and total energy E. This block is now replaced with a new block of mass m' = 3 m, on the same spring, and set into simple harmonic motion with amplitude x'm = 2 xm. The total energy of the oscillator is now:
(a) 4/3 E
(b) 2 E
(c) 4 E
(d) 9 E
(e) 13 E