The surface area of the rectangular prism is
[tex]A=2\lbrack l\text{ }\times w+l\times h+w\times h\rbrack[/tex]From the given figure
l = 5 km, w = 3 km, h = 4 km
Substitute them in the rule above
[tex]\begin{gathered} A=2\lbrack5\times3+5\times4+3\times4\rbrack \\ A=2\lbrack15+20+12\rbrack \\ A=2\lbrack47\rbrack \\ A=94 \end{gathered}[/tex]The surface area is 94 km^2
