I hope this can help you:
total K = (1/2)*m*v^2 + (1/2)*I*w^2
actually you don't have to use I = 0.688 which is given if you know the I of the disk is (1/2)*m*r^2.
plug all in, find out K = 3/4 * m * v^2
next,
the work does on the wheel also equals to the total K above. W = F*s =...
i'll give you somemore hints. Helps this can help:
K1 + U1 = K2 + U2
where K1 = (1/2)*I*w^2 + (1/2)*m*v^2
the same to K2
for the ball: I = (2/5)*m*r^2
You should choose OGPE at the bottom where the ball first starts (It's just easier ). So U2 = mgh.
Use conservation energy to...