For the first 3% of Pam's salary, her employer matches 100% of her 401(k) contributions, and from 3% to 12%, Pam's employer matches 50% of her 401(k) contributions. Pam'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. $3600  C. $2250  D. $1800