conservation of energy physics question?

A factory worker accidentally releases a crate of mass m that was being held at rest at the top of a ramp with length d which is inclined at angle θ to the horizontal. The coefficient of kinetic friction between the crate and the ramp, and between the crate and the horizontal factory floor, is μk. (use g where applicable). (Use any variable or symbol stated above along with the following as necessary: g for the acceleration of gravity.)

how i thought to get the answer:

total energy at the top of the ramp = U (potential energy) = mgh

and total energy at the bottom of the ramp =

K (kinetic energy) - work done by friction = 1/2 * m * v^2 - mu * m * g * d * cos(theta)

so conservation of energy says energy at the top must equal energy at the bottom thus:

mgh = 1/2 mv^2 - mu *mgdcos(theta)

solving for v i get:

sqrt(2*g*d*(sin(theta) + mu * cos(theta)))

by the way i subbed d*sin(theta) for h, as im not allowed to use h

where did i go wrong???