Need help finding the volume of this I got it wrong , 96m^3 is not the answer.

Answer:
B = 1/2 (4) (5x8)
B = 1/2 (4) (40)
Then I multiplied 40 and 4 and got 160.
Then I divide 160 by 2 which is 80.
Then we find the volume by setting up this equation.
V = 1/3 (80) (18)
I multiplied 80 and 18 and got 1440.
I then divide it by 3 and got 480.
Answer 480 m^3