Betty files as head of household in 2015. She had a taxable income of $80,000, including the sale of stock she held for investment for two years for a $15,000 gain. Betty sold no other assets during the year, and she did not have any capital loss carryovers.

a. What is betty's 2015 tax liability?

b. What would Betty's 2015 tax liability be if he had held the stock for 10 months?