Devon studied the composite figure.
(picture 1)
he believed the surface area, in square units, could be found by simplifying the expression
(picture 2)
what error did devon make?

a. he used 26 instead of 24 as the slant height of one set of lateral faces.
b. he omitted the rectangle where the upper and lower solids join together.
c. he included the 34 by 20 base of the figure.
d. he believed the upper part of the figure was a pyramid instead of a prism.