For the first 6% of Britney's salary, her employer matches 100% of her 401(k) contributions, and from 6% to 12%, Britney's employer matches 50% of her 401(k) contributions. Britney's salary is $30,000, and last year, she contributed $4000 to her 401(k) plan. What was her employer's contribution to the 401(k)?
A. $4000
B. $1800
C. $3600
D. $2700