Flax Corp measures its activity in terms of square feet of flooring installed. Last month, the budgeted level of activity was 1,180 square feet and the actual level of activity was 1,270 square feet. Flax budgets for supply costs at $1,200 plus $3.50 per square foot. The actual supply cost last month was $5,800. Flex's spending variance for supply costs is closest to: a. $155 F O b. $470 F C. $470 U d. $155 U