David, a 69-year-old single taxpayer, received $18,000 in social security benefits in 2016. He also earned $13,000 in wages and $6,200 in interest income, $3,000 of which was tax-exempt. What percentage of David's benefits will most likely be considered taxable income? 1) none 2) up to 50% 3)up to 85% 4) up to 100%