Installment Sales (The answers are $5,000, $10,000 and 50% but I don't understand how to get these answers)

Q: "During the current year, Mr. C sold property that had an adjusted basis to him of $19,000. The buyer assumed Cs existing mortgage of $15,000 and agreed to pay an additional $10,000 consisting of a cash down payment of $5,000, and payments of $1,000, plus interest, per year for the next 5 years. Mr. C paid selling expenses totaling $1,000. What is Cs gross profit? What is the total contract price? What is Cs gross profit percentage?"

Please show work (especially for the contract price). Thank you!