for the implicit integration I got:
the vertical tangent would at points at which y' goes to infinity.
that happen when the right-hand side has singularities, that is, the denominator is 0:
so the two points y above have a vertical tangent.
I would say B but I can't see the question very well.
The answer would be: There were 2 chefs and 13 customers.
In the first bag, picking a black marble would be impossible.
The second bag would be likely.
The third bag would be unlikely.
hope this helps!