According to Hooke's Law, the force needed to stretch a spring is proportional to the distance the spring is stretched. If a force of 180 newtons stretches a spring 6 cm, what is the direct variation equation for this spring? If a force of 420 newtons was applied, what is the distance the spring will be stretched? Select all answers that apply.

[mark all correct answers]

a) f=6x
b) f=30x
c) f=70x
d)x=14
e) x=31.5
f) x=2.6