23,000 * 12/100 = 23,000 * 0.12 = 2,760$
You would make 2,760$ in commisions
I'd say option b, you can learn why by isolating x.
F(1) = -f(0) +5 = -3 +5 = 2
f(2) = -f(1) +5 = -2 +5 = 3
f(2) = 3
_____
The sequence appears to alternate between 3 and 2.