I think 4 and 6 lcm is 12
It's basically multiplication by 3. 3x3 9x3 27x3 etc
ANSWER
D.

EXPLANATION
The given function is

Comparing to the general form of a trigonometric sine function,


The amplitude is absolute value of A


The period is given by



is a shift to the right of 4 units.
and

is an upward shift of 9 units
Therefore the phase shift is (4,9).
The correct answer is D
So it decreases by 11% which means by the next year it's worth 89% of the original price, write 89% like a decimal. then put it to the power of 4 (4 years) and multiply by the original number
.89 ^ 4 * 12250 = 7685.92