i'm not very good at physics and i have an exam tomorrow!!

Question

for the first one do i use the formula F=-Kx to make the answer -4500 ?

and for the second i really have no idea what formula to use

what is the value for k if a spring stretches 0.4m when submitted to a 1800N force?

How much force is needed to keep a 23 kg box moving at a constant velocity across a warehouse floor if the coefficient of friction between the box and the floor is 0.88?

Answer 1

k=force/distance

moving at a constant veloicty? Well you have to supply force equal to friction: mg*mu

Answer 2

k=F/x
=1800/0.4
=4500 N/m