AP Physics 1 3.2: Work Done by a Force

(12 points, suggested time 25 minutes)
A block is initially at position x=0 and in contact with an uncompressed spring of negligible mass. The block is pushed back along a frictionless surface from position x=0 to x=-D, as shown above, compressing the spring by an amount $\Delta x=D$. The block is then released. At x=0 the block enters a rough part of the track and eventually comes to rest at position x=3 D. The coefficient of kinetic friction between the block and the rough track is $\mu$.

Which aspects of the student's reasoning, if any, are incorrect? Explain how you arrived at your answer.