One question of interest is how sensitive your profit-planning model is to the assumption regarding sales mix. In order to address this question, you decide to prepare a table in which you disclose the percentage change in the weighted average contribution margin per unit for each 1% absolute change in the sales mix for service line #1 over the range 20% to 30% inclusive. Use the resulting wieghted average contribution margin to calculate the total breakeven units and the percentage change in the breakeven volume from the base case