According to the general equation for conditional probability, if p(a^b)=4/7 and p(b)=7/8, what is p(a b)?

Ms. ortiz sells tomatoes wholesale. the function p(x)=-80x^2+320x-10, graphed below, indicates how much profit she makes on a load of tomatoes if she makes on a load of tomatoes if she sells them for 4-x dollars per kilogram. what should ms. ortiz charge per kilogram of tomatoes to make on a load of tomatoes?