Just realized this is a trapezoid and i don't know much about trapezoids and area so i have no clue how to attempt a three dimensional one. explain if you can

In stepmber, daniel and justin opened a business. during their first three months of business, their average monthly profit was $51. if during their first month, they lost $29, and during their second month, they gained $115, what was their profit or loss for their third plzzz i will give you 299 points