Utilizing the information about After$-$Tax Savings Rate of Return in the "Figure It Outl" Box on page $122$ in textbook, answer the following questions: $[$Make sure to show your work$]$

a$.$ Opal earned $6\%$ in her savings account. If she is in the $25\%$ tax bracket, what is her after$-$tax savings rate of return?

b$.$ What would be the after$-$tax value of $$100$ earned in interest for Opal who is in the $25\%$ tax bracket?