Volume of a prism = Bh
B = area of the base
h = height
B = 1/2 (base1 + base2) x height
B = 1/2 (9+6) x 8
B = 1/2 (15) x 8
B = 4 x 15
B = 60
Volume = 720
720 = B x h
720 = 60 x h
h = 12
So the height or length is 12mm.
Surface Area = 2B + 2P
Where
B is the area of the base
P is the perimeter of the base
We already know that B= 60
P = 9 + 10 + 6 + 8
P = 33
So
SA = 2*60 + 2*33
SA = 120 + 66
SA = 186
The surface area is equal to 186mm^2.