Answer:
Both Triangle faces' area are 36. You'll need to multiply 36 by 2. now you need to multiply 4 by 20 which then would be 400. multiply 400 by 2 which would be 800. Now going back to 36 by 2 would be 72. Now 72·400=28800.
Explanation:
Since it's a triangle prism , you find the area of the 2 triangle faces and than multiply the 2 faces and then multiply the the rest of the other numbers