Last year, Flip Flop Shoe Company had gross margin of $600,000 on $1,000,000 of sales revenue and had selling and administrative costs of $250,000. The company started the year with $1,500,000 of operating assets and ended the year with $1,300,000 of operating assets. Compute the companys margin.

A : 30%

B : 25%

C : 35%

D : 60%