Answer:
A.\ \ r(d)=-100(d-25)^2+122,500
Hope this helps!



Stationary points occur where the derivative is zero. The denominator is positive for all

, so we only need to worry about the numerator.


for all

, so we can divide through:

But

for all

, so this function has no stationary points...
I suspect there may be a typo in the question.
To answer this, let the 3 sides of the regular sized rectangular box be x, y, and z.
When we double all the sides, the new sides have lengths 2x, 2y, and 2z, respectively.
Since the regular box (with dimensions x,y, and z) have 750 toothpicks, we can write

Similarly we can write for the jumbo box as,

which is equal to 
So this is 8 times the original of
. Hence the jumbo box will have 8 times 750 number of toothpicks.
ANSWER:
toothpicks