Deepansh
You are right about 3908-168=3740. But in the question there was nothing written like " All the cakes were to be scrapped/wasted/nil salvaged". It was very intelligently written " No carry over of Cake". Now, if one person assumes that unsold cakes were used in some other area, then only penalty will be applicable.
But again, it was given that Variable cost is xxx .So, this was the hint for 3740. If all the cakes assumed to be of no value/ got wasted.
Now, in every question in PM, there is written that Stock will get wasted if not sold. Then cost is taken for consideration.
So, it can go in both ways. But one should give proper assumption.
FYI My answer was 3908. I ignored the VC. 
2nd part was 3854.
So, I hope we, 3908's, get atleast 4 out of 8.