Kirsten is 29 years old and just started a new job at a company that offers a 401(k) plan. Her annual salary is $36,000, and she is paid biweekly. Kirsten would like to have $700,000 in her 401(k) when she reaches age 65. Her company does not offer any matching, and she expects that her investments can earn 7.5%. What percent of salary should Kirsten contribute to her 401(k) to reach her goal?