Give me an example of Antonella works for a company that pays an annual year$-$end bonus. Assume that Antonella expects to receive a $$18,000$ bonus on December $28$th of this year, her tax rate is $28\%,$ and her after$-$tax rate of return is $7\mathrm{.}0\%.$

a$.$ If Antonella$$s employer paid her bonus on January $1$st of next year instead of in December, how much would this action save Antonella in today$$s tax dollars?

b$.$ If Antonella$$s tax rate increase to $32\%$ next year, how much would she save or lose by deferring until January?