In order to calculate the surface area, consider the following formula:
S = 2l·w + 2l·h + 2w·h
where
w: width = 7 m
l: length = 9 m
h: height = 5 m
replace the previous parameters into the formula for S:
S = 2(9 m)(7 m) + 2(9 m)(5 m) + 2(7 m)(5 m)
S = 126m² + 90m² + 70m²
S = 286m²
Hence, the surface are of the given figure is 286m²