Each of a company's several product lines has a different contribution margin ratio. Total sales in 2014 were 20% higher than total sales in 2013. Total contribution margin for 2014 will be:

a. the same as it was in 2013, regardless of changes in sales mix.

b. 20% higher than it was in 2013, regardless of changes in sales mix.

c. more than 20% higher than it was in 2013, if the sales mix changes and proportionately more high contribution margin ratio products are sold in 2014 than in 2013.

d. less than 20% higher than it was in 2013, if the sales mix changes and proportionately more high contribution margin ratio products are sold in 2014 than in 2013.