Reardon Retail Company consists of two stores, A and B. Store A had sales of $80,000 during March, a contribution margin ratio of 30%, and a segment margin of $11,000. The company as a whole had sales of $200,000, a contribution margin ratio of 36%, and segment margins for the two stores totaling $31,000. If net operating income for the company was $15,000 for the month, the traceable fixed expenses in Store B must have been:

a. $16,000

b. $20,000

c. $31,000

d. $28,000