4. (A) Leah, a widow, is retired and receives $20,000 interest income and dividends and $10,000 in Social Security benefits in 2018. >How much of her Social Security benefits are taxable? (B) Same facts as above. Leah is also considering selling a stock at an $8,000 gain. >What will be the increase in Leah's taxable Social Security benefits if she sells the stock