Answer:
C(r) is the area of the base of a cylindrical tank with radius r.
We know that this area is:
C(r) = pi*r^2
S(x) is the area of the square base where x is the side length of the base.
S(x) = x*x
Now, we have the expression:
S( C(r)) wich means that we are evaluating the function S(x) in the point x = C(r)
Now, we have a problem here.
In S(x), S(x) is in units of area, and x is in units of length.
And the same for C(r), C(r) is in units of area, and r in units of length.
then we can not have x = C(r)
Then this expression does not represent anything, because the units do not match, so it has no physical sense.
°