Finding the coefficient of sliding friction? HELP!?

Question

there are two questions

A box weighing 18 newtons requires a force of 6 newtons to drag it.

What is the coefficient of sliding friction?

here is the second question

a box weighing 18 newtons is coated with Teflon and now requires a force of 3 newtons to drag it

what is the coefficient of friction?

I need the answer (and mabye how to figure out the answer) thanks!

Answer 1

friction=(coef. of sliding friction)*(weight)

If the box can be dragged, that means the friction is just lower than the dragging force (or, for the borderline case, just equal to it):

friction=6 N  (for the first case)

friction=3 N (for the second)