What is the equation for the attached picture?

15) METER READINGS CURRENT CHARGES Meter NunvSizs 50002401/6/8"X3/4 Current Reading (07/17/2018) 560.19 Water Service: Previous Reading (16/15/2018) 547.09 2018 Water Used Charge @ $ 3.140 X 13.04 CCF 40.85 Water UBe CCF 14.04 (MDC Water rate is 0.0042 Cents per US-Gaston) 2019 Water Customer Spec Charge 14.38 Sub Total: $65.93 Sewer Service: 2018 Sewer Customer Sryc Charge 3.00 Sub Total: $3.00 Federal / State Regulatory Compliance Fees: 2018 CWP Charge @ $ 3.800 X 13.04 CCF 49.55 2018 DPH Drinking Water Fee 0.33 Sub Total: $49.88 TOTAL CURRENT CHARGES $108.81 received this water bill from the MDC for the period June 15 to July 17, 2018. a) What amount (in dollars) of the total charges of $108.81 represent variable costs? b) What amount (in dollars) of the total charges of $108.81 represents fixed costs