managers should never forget that variable and fixed cost-behavior patterns are valid for linear cost function only within a given relevant range. outside the relevant range, variable and fixed cost-behavior patterns change, causing cost to become nonlinear(nonlinear means the plot relationship on a graph is not a straight line).for example,exhibit 10-2 plots the relationdhip (over several years) between total direct manufacturing labor costs and the number of snowboards produced each year by ski authority at its vermont plant. in this case, the nonlinearities outside the relevant rang occur because of labor and other inefficiencies (first because workers are learning to produce snowboards and later because capacity limits are being stretched). knowing the relevant range is essential to properly classify costs