After graduating from dental school two years ago, Dr. Dorothy Taylor 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 In January of this year, she had to replace the outdated autoclave equipment she inherited from the previous dentist.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 $7,040 February 750 6,425 March 920 7,511 April 950 7,955 May 1,150 8,785 June 900 7,448 July 1,050 8,670 August 975 7,909 (a) Using the high-low method, what is the variable cost of sterilizing an instrument using the new equipment? (Round answer to 2 decimal places, e.g. 52.75.) $ Variable cost per instrument