There the same thing they both weigh the same thing hope it helps and have a great day!
Looks like you have most of the details already, but you're missing one crucial piece.
is parameterized by
for 
and 
, and a normal vector to this surface is
with norm
So the integral of 
is
The key term here is inverse variation - that is, two or more variables must multiply to a certain product.
So, let's multiply 12 and 8. We get 96.
The correct pair must contain factors of 96.
16 and 6 are factors of 96, so the answer is (D).
The equation you can use to relate L to D uses the information in the first part of the problem. First, if we just add 4 miles every day (ignoring the other piece), the length of the road would be 4 times the number of days, or L = 4D. But since we started with 57 miles built, we have to add that in order to get the total length, so the equation would be:
L = 4D + 57
You can use this question to find any value of L or D if you know one of them. According to the questoin, we know the crew worked 34 days (or D). So if you plug in 34 for D you'll get:
L = 4(34) + 57 ->
L = 136 + 57 ->
L = 193
