Pisa Pizza, a seller of frozen pizza, is considering introducing a healthier version of its pizza that will be low in cholesterol and contain no trans fats. The firm expects that sales of the new pizza will be $$18$ million per year. While many of these sales will be to new customers, Pisa Pizza estimates that $32\%$ will come from customers who switch to the new, healthier pizza instead of buying the original version.

a$.$ Assume customers will spend the same amount on either version. What level of incremental sales is associated with introducing the new pizza?

b$.$ Suppose that $47\%$ of the customers who will switch from Pisa 'Pizza's original pizza to its healthier pizza will switch to another brand if Pisa Pizza does not introduce a healthier pizza. What level of incremental sales is associated with introducing the new pizza in this case?