The answer is 30720
A = P * rⁿ
A - the final population
r - the growth rate
P - the initial number of bacteria
n - the number of hours
We know:
A = ?
r = 2 (it doubles)
P = 15
n = 12
After 11 hours
A(11) = 15 * 2¹²
A(11) = 15 * 2048
A(11) = 30720
After 12 hours
A(12) = 15 * 2¹²
A(12) = 15 * 4096
A(12) = 61440
<span>How many bacteria are grown during the 12th hour?
A(12) - A(11) = 61440 - 30720 = 30720</span>
The answer to the question they gave you is D

The surface element is

and the integral is


###
To compute the last integral, you can integrate by parts:



For this integral, consider a substitution of




and the result above follows.
1 -since everything includes 4a, we can factor that to get 4a(a-4b^3+2b^2c)
2 - since 5 and 3 add to 8 and multiply to 15, we can do (n+5)(n+3)
3 - since -5 and -4 add to -9 and multiply to 20, we can do (g-5)(g-4)
4 - since -10 and 3 add to -7 and multiply to 30, we can do (z-10)(z+3)
5 - we can factor out 4y to get 4y(y^2-9).
I got the numbers in 2, 3, and 4 with a guesstimating and checking approach