Answer: $6.2
Explanation: Contribution margin is the amount of revenue left after paying for the variable cost, it can be formulated as follows :-
contribution = sales - variable cost
In case of Limeade:-
sale price = $22.10
Variable cost = $15.90
so, putting the values into equation we get :-
contribution per foot = $22.10 - $15.9 = $6.2