MHB Friction Mechanics: Solving for Block's Speed at Point A

[Shah 72]

A wooden block of mass 3.5kg is sliding up a rough slope and passes a point A with speed 20m/s. The slope is at 29 degree to the horizontal. The block comes to rest 25m up the slope. Find its speed as it passes point A on the way down.
I calculated coefficient of friction = 0.554.
U=20m/s v= 0 and s= 25m.
By using v^2= u^2+2as, I got a= -8m/s^2.
I can't calculate after this.
Pls help

 

[skeeter]

upslope …

$a = \dfrac{0^2-20^2}{50} = -8 \, m/s^2 = -10[\sin(29)+\mu\cos(29)] \implies \mu = 0.36$

try again …