Answer:
A
Explanation:
Remark
One of the handiest things to know in physics is something called dimensional analysis.
Look at the answers you are given. All of them are in N/m. That means 2 things.
No conversions are necessary
You divide Newtons / meters. You don't need to worry too much about a formula.
But if need a formula, it is F = k * x and you need k
x = 3.5 m
F = 20.0 N
k = F / x
k = 20.0/3.5
k = 5.71 to 3 places.
