Human hands covered with cotton fabrics impregnated with the insect repellent DEPA were inserted for 5 minutes into a test chamber containing 200 female mosquitoes. The function f(x) = 26.48 - 14.09 ln x gives the number of mosquito bites received when the concentration was x percent.

(a) Graph f (x) and f′(x) for 0 < x ≤ 6.

(b) How many bites were received when the concentration was 3.25%?

(c) What concentration resulted in 15 bites?

(d) At what rate is the number of bites changing with respect to concentration of DEPA when x = 2.75?

(e) For what concentration does the rate of change of bites with respect to concentration equal -10 bites per percentage increase in concentration?