A Mass of 4 $\times$ 10² N/m

Multiple Choice

A mass of 4.5 kg causes a 15-cm extension of a spring. Assuming that the acceleration of gravity is 10 m/s², the force constant of the spring is

A) 3.0 N/m.
B) 7.0 N/m.
C) 30 N/m.
D) 3.0 $\times$ 10² N/m.