height of the prism = ±√(7.8^2 -5.4^2) = ±5.6285cm (5s.f.) (rej. - 5.6285 since height > 0cm)
volume of the prism = 1/2 x 5.4 x 5.6285 x 16 = 243cm^3 (3s.f.)
This is a question on mensuration. If you wish to venture further into it/understand this topic better, you may want to follow my Instagram account (learntionary), where I post some of my own notes on certain topics and also some tips that may be useful to you :)
