Answer: The cost is $600
Step-by-step explanation: The wall is a rectangle whose area is calculated as:
S = 8.5 x 2
S = 17
However, there is a door on the wall which won't be whitewashed so:
Area of door:
[tex]S_{d}[/tex] = 2 x 1
[tex]S_{d}[/tex] = 2
Whitewashed area will be
S - [tex]S_{d}[/tex] = 17 - 2
S - [tex]S_{d}[/tex] = 15m²
To whitewash the wall, it costs $40 per each m², so:
Cost = 15*40
Cost = 600
To whitewash the wall, it will cost $600.