A rectangular solid has length $8.5$, width $5$, and height $10$. What is its total **surface area**?

A rectangular solid has $6$ rectangular faces, organised as $3$ pairs of identical faces. The total surface area is $A = 2(\ell w + \ell h + w h)$. Compute each pair: - $\ell w = 8.5 \times 5 = 42.5$ - $\ell h = 8.5 \times 10 = 85$ - $w h = 5 \times 10 = 50$ Sum: $42.5 + 85 + 50 = 177.5$. Double (because each face occurs in two opposite copies): $A = 2 \times 177.5 = 355$. - Trap B ($177.5$) stops at the half-sum without doubling. - Trap D ($425$) returns the **volume**. - Trap A ($135 = 5 + 50 + 80$) miscombines dimensions.