Jennifer got a box of chocolates. the box is a right triangular prism shaped box. it is 7 inches long, and the triangular base measures 2 in x 3 in x 4 in. what is the surface area of the box of chocolates? (show work)

The first thing we should know is the area of the triangular base.
 Triangular base area: 
 A1 = root (s * (s-a) * (s-b) * (s-c))
 Where, s is the semi-meter of the triangle:
 s = (a + b + c) / 2
 a, b, c: sides of the triangle.
 Substituting:
 s = (2 + 3 + 4) /2=4.5
 A1 = root (4.5 * (4.5-2) * (4.5-3) * (4.5-4))
 A1 = 2.90
 Then, you must know the area of each rectangle associated with each side of the triangular base.
 Rectangle area 1:
 Ar1 = (a) * (l)
 Ar1 = (2) * (7)
 Ar1 = 14
 Rectangular area 2:
 Ar2 = (b) * (l)
 Ar2 = (3) * (7)
 Ar2 = 21
 Rectangular area 3:
 Ar3 = (a) * (l)
 Ar3 = (4) * (7)
 Ar3 = 28
 Finally the surface area is:
 A = Ar1 + Ar2 + Ar3 + 2 * A1
 A = (14) + (21) + (28) + 2 * (2.90)
 A = 68.8 in ^ 2
 
 the surface area of the box of chocolates is 
 A = 68.8 in ^ 2