The phone bill for B Company consists of both fixed and variable costs. Refer to the 4-month data below and apply the high-low method to answer the question. Minutes Total Bill January February200 March April 320 $2,880 260 $2,725 300 $2,760 What is the variable cost per minute? a) $10.00 b) $3.20 c) $9.00 d) $4.00