Inspection costs at one of Ratulowski Corporation's factories are listed below: Units Produced Inspection Costs April 906 $ 16,312 May 951 $ 16,700 June 912 $ 16,365 July 896 $ 16,210 August 918 $ 16,394 September 903 $ 16,280 October 920 $ 16,432 November 860 $ 15,850 December 899 $ 16,238 Management believes that inspection cost is a mixed cost that depends on units produced. Using the high-low method, the estimate of the fixed component of inspection cost per month is closest to: