What is the acceleration and time for a block on an inclined plane?

[rumblef1sh]

I am stuck on a problem from the 5 Steps to a 5: AP Physics B&C book and would really appreciate anyone's help.

Homework Statement

Determine (a) the acceleration of the block down the plane and (b) the time for the block to slide to the bottom of the plane.

http://02.edu-cdn.com/files/static/mcgrawhillprof/9780071623209/INCLINED_PLANES_08.GIF

Homework Equations

F=ma
F, gravity = mg
F, friction = umg
Kinematic equation ?

The Attempt at a Solution

Fx, up the plane = mgsin25 + umgcos25 = 204 N
a = F/m = 204/30 = 6.8 m/s^2
Fx, down the plane = mgsin25 - umgcos25 = 44 N
a = F/m = 44/30 = 1.5 m/s^2

I tried using x = Vot + 1/2 at^2 (x = 20 m, Vo = 3m/s) and v = Vo + at (v = 0, Vo = 3 m/s) to solve for time, but my answers were way off on both attempts.

 

[Panphobia]

If the question says the mass is going 3 m/s up the plane, and the a) part asks for the acceleration DOWN the plane this means that x != 20, but it is going to be 20 added to the distance traveled by the mass until it changes direction. I hope that helped.