Tandra's grandparents would like to sell her their second home in 10 years for the present market price of $160,000. Tandra decides to pay them cash in 10 years from her retirement savings, which she plans to grow by $700 every month. She also has saved $2,000 up to now. What interest per year will her account have to earn to have enough money in it to pay her parents?

Please solve clearly and correctly. Thank you.