Which of the following is derived unit?
a: g (grams, mass)
b: m (meters, length)
c: s (seconds, time)
d: m2 (square meters, area)

Ahanging spring stretches by 35.0 cm when an object of mass 450 g is hung on it at rest. in this situation, we define its position as x = 0. the object is pulled down an additional 18.0 cm and released from rest to oscillate without friction. what is its position x at a moment 84.4 s later? express your answer in cm.