The total number of passengers (T) in the jet is 380, out of which 34 are in first class (f), so the number of passengers in the coach (c) is calculated as,
Also given that cost of first class ticket (Cf) is $690, and the cost of a coach ticket (Cc) is $331.
So the gross amount of a full plane is calculated as,
Thus, the airline will gross $137986 if the plane is full.