A ball of mass of 10 g is hung from the end of a light vertical spring and set oscillating with an amplitude of 10 cm. The period of the oscillation is 1 s. If the ball is now replaced by another with a mass of 40 g and again set oscillating with the same amplitude, its new period of oscillation will be,
(a) 1 s.
(b) 2 s.
(c) 4 s.
(d) 8 s.