High-low method for a service company Sierra Railroad Inc. decided to use the high-low method and operating data from the past six months to estimate the fixed and variable components of transportation costs. The activity base used by Sierra Railroad is "gross-ton miles," which is the total number of tons multiplied by the miles moved. Transportation Costs Gross-Ton Miles January $1,216,200 347,000 February 1,356,000 388,000 March 958,300 251,000 April 1,300,000 375,000 May 1,090,400 302,000 1,397,900 408,000 June