What is the Correct Acceleration of a Book on an Inclined Plane with Friction?

[Terraist]

Homework Statement

The 1.92 kg physics book shown is connected by a string to a 450.0 g coffee cup. The book is given a push up the slope and released with a speed of 2.58 m/s. The coefficients of friction are μs = 0.457 and μk = 0.166. What is the acceleration of the book if the slope is inclined at 21.2°?

Homework Equations

f=ma

c is cup
b is book

The Attempt at a Solution

Alright I've tried pretty much goddamn everything (including a solution from a textbook) and I still get the wrong answer. Here's the best I can do.

f = ma

-m_cg - u_k(m_bg cos x) - m_bg sin x = -ma

a ={0.450(9.8) + 0.166 (18.8 cos 21.2) + 18.8 sin 21.2}/ (1.92 + 0.450)

a = 5.96 m/s² Wrong!

 

[TxRationalist]

where are you taking the frictional force and V0 into consideration in your equations?