Ms$.$ Teague incurred a $$28,000$ expense and her marginal tax rate is $30\%.$

Based on the above information, which of the following statements is true?

a$.$ If the expense is nondeductible, Ms$.$ Teague$$s after$-$tax cash flow is zero.

b$.$ If only $40\%$ of the expense is deductible, Ms$.$ Teague$$s after$-$tax cash flow is $($$$24,640).$

c$.$ If the expense is deductible, Ms$.$ Teague$$s after$-$tax cash flow is $($$$8,400).$

d$.$ Statements b$.$ and c$.$ are true.

e$.$ None of the above is true.