1, both functions are linear
In the given question, it is already mentioned that Pam takes 15 minutes to type 2.5 pages. this information should be used as the main information for reaching the desired answer.
Pam typed 2.5 pages in = 15 minutes
Then time taken by Pam to type 23 pages = (15/2.5) * 23
= 345/2.5
= 3450/25
= 138
So Pam will take 138 minutes to type 23 pages
The answer is A, the first one :)
If

then

Differentiating with respec to
gives


So
is indeed conservative, and
