The coefficient of friction between the block and plank is $\mu$ and its value is such that the block becomes stationary with respect to plank before it reaches the other and end Then:

The work done by friction on the block is equal to change in KE
 $W_1=\frac{1}{2}m{v}^2-\frac{1}{2}m{v}_0^2=\frac{1}{2}m\left(\frac{m{v}_0}{m+M}\right)-\frac{1}{2}m{v}_0^2=-ve$

So, choice (1) is correct.
The work done by friction on the plank
 $W_2=\frac{1}{2}m{v}^2-0=+ve$
So choice (2) is correct.
Net work done by friction