Lacourse Inc.'s inspection costs are listed below: Units Produced Inspection Costs January 434 $ 6,138 February 384 $ 5,643 March 453 $ 6,353 April 468 $ 6,491 May 410 $ 5,893 June 385 $ 5,646 July 460 $ 6,418 August 411 $ 5,906 Management believes that inspection cost is a mixed cost that depends on units produced. Using the least-squares regression method, the estimate of the variable component of inspection cost per unit produced is closest to: