fill in the blanks to complete the formula for the surface area of a triangular prism.
the surface area of a triangular prism is S.A. = ___ + ( S1 + S2 + S3 ) ___
+ 2 ( A + B + C )
where S1, S2, and S3 are the areas of the three triangular faces, and A, B, and C are the lengths of the three sides of the triangular base.