Kathleen and Glenn decide that this is the year to begin getting serious about saving for their retirement by participating in their employers' 401(k) plans. As a result, they each have $3,000 of their salary set aside in their qualified plans. If an amount is zero, enter "O". Click here to view Exhibit 12.3, "Saver's" Credit Rate and AGI Thresholds. a. Calculate the credit for certain retirement plan contributions available to Kathleen and Glenn if the AGI on their joint return is $35,000. $ b. Kathleen and Glenn persuade their dependent 15-year-old son, Joel, to put $500 of his part-time earnings into a Roth IRA during the year. His AGI is $7,000. What is the credit for certain retirement plan contributions available to Joel? $