Physics help with spring force?

Question

When the block is pulled out to x = +5.0 cm, we must apply a force of magnitude 370 N to hold it there. We pull the block to x = 14.0 cm and then release it. How much work does the spring do on the block when the block moves from xi=+6.0 cm to (a)x= +3.0 cm, (b)x= -3.0 cm, (c)x= -6.0 cm, and (d)x= -9.0 cm?

Answer 1

Energy in the spring
Ps=0.5kx^2

Well first what is k
k=F/d= 370/5 N/cm

So if the block moves from
a) +6.0 to +3.0 the d= 6-3=3

Ps= 0.5 (370/5) (3)^2....

b) a) +6.0 to -3.0 the d= 6- (-3)=9
and so on