On the horizontal line P=6, it looks like the values W=10, 11, 12 may be in the doubly-shaded region. We know that each of those will give a purchase of at least 16 fruits, but we don't know if the budget constraint is met with 12 watermelons. You'd have to check prices to make sure.
If 11 is among the choices, that is the answer I'd choose.