Duke and Pat Collins have adjusted gross income of $500,000 for 2010. They have itemized deductions of $20,000 consisting of $8,000 in medical expenses that exceed 7.5% of adjusted gross income, $3000 in property taxes, $4000 in housing interest, and $5000 in miscellaneous itemized deductions that exceed 2 percent of adjusted gross income. What is the amount of their itemized deductions?