Triangular prism and net diagram of prism with faces labeled A, B, C, D, and E. Length 18 in., width 10 in., height 12 in. Triangular base A and Triangular base D are congruent. Rectangular face B and Rectangular face C are congruent. Rectangular face E. Area of base A- A equals one-half bh equals one-half times 10 times what equals what. Area of bases A and D- A sub A and D equals 2 times what equals what.