After graduating from dental school two years ago, Dr. Donna Clark purchased the dental practice of a long-time dentist who was retiring. In January of this year, she had to replace the outdated autoclave equipment she inherited from the previous dentist. Now, as she is preparing her budget for next year, she is concerned about understanding how her cost for sterilizing her dental instruments has changed. She has gathered the following information from her records: Month Number of instruments used Total autoclave cost January 850 $8,335 February 750 7,650 March 920 8,854 April 950 9,320 May 1,150 10,290 June 900 8,777 July 1,050 10,105 August 975 9,291 What is the cost formula that Dr. Clark should use for estimating autoclave sterilization costs for next year's budget? Formula of total cost