Required information [The following information applies to the questions displayed below.] Grady received $8,480 of Social Security benefits this year. Grady also reported salary and interest income this year. What amount of the benefits must Grady include in his gross income under the following five independent situations? (Leave no answer blank. Enter zero if applicable.) b. Grady files single and reports salary of $22,770 and interest income of $670. Amount to be included in gross income my