Apiece for a board game is shaped like a triangular prism. the piece is 18 millimeters long. the base of the piece is an equilateral triangle with 10 millimeter sides and a height of 9 millimeters. find the surface area of the game piece

We can solve for the surface area of the triangular prism using the formula below:
SA=bh + (s1+s2+s3) H
where b for the base, h and H for the height while s1, s2 and s3 for the length of the sides of the equilateral triangles.
Solution is shown below:
SA=10*9+(10*10*10) *18
SA=90+(1000*18)
SA=1,620,000 u²