I believe that the question is assuming this is taking place over one month here is what I think you would do.
1) 75/12.5 = 6
2) add that answer to 75, so 75+6, and you get 81
Yes they do, Hope this helps :p
The given plane, 
, has normal vector 
. Any plane parallel to this one has the same normal vector.
Let 
be any point in the plane we want. The plane contains the point (1, 1, -1), so an arbitrary vector in this plane is
and this is perpendicular to 
.
So the equation of the plane is
or equivalently,
What you do is you do 93 x 81.
93
x 81
------------
93
+ 7440
-------------
7,533
That's the square footage. Hope it helps!
No Nothing Further Can Be Done
