Dr. Armstrong performs a certain cosmetic dental procedure at her dentistry clinic. Her monthly fixed operating costs are $12,000, while her after-tax operating income is $8,000 when she performs 200 such procedures in a month. Dr. Armstrong's before-tax operating income is subject to a marginal tax rate of 60%. Required: a) What is the margin of safety percentage for Dr. Armstrong, assuming she performs 200 procedures? b) What is the degree of operating leverage for Dr. Armstrong, again assuming she performs 200 procedures