Can you please explain these two questions to me?

Suppose the population size of a predator is given by P (x) = 0.006x2 + 0.005x, where x represents the population of its prey. If the population of the prey is 10,000 at the first of January and is reduced to 6,000 by May 1 of the same year, how fast is the population of the predator changing on July 1 of the same year? Assume prey population is linear with respect to time.
what I did was take the derivative of P(x) then I subtracted 10000 from 6000 to get 4000, then I plugged that back into the derivative function and got 48.005. I was off by a 1000 can some on please explain?

(a) Declining at a rate of approximately 1,000 per month.
(b) Declining at a rate of approximately 1,200 per month.
(c) Declining at a rate of approximately 48,000 per month. (d) Declining at a rate of approximately 72,000 per month.
(e) Declining at a rate of approximately 120,000 per month.

A bacteria culture has 1,000 bacteria at 7:00AM one day. By 9:00AM that day there are 1,500 bacteria. Supposing that the number of bacteria grows exponentially, how many bacteria will there be at 11:00AM that day?

I used the Pert formula, 1500=1000e^r2/24 then took the ln of both sides and got ln 1500= 1000 r(2/24) and I get 609.435 what am I doing wrong?

(a) 2,000 (b) 2250 (c) 2500 (d) 2756 (e) 25629