A man with $20,000 to invest decides to diversify his investments by placing S10,000 in an account that earns 4.2% compounded continuously and $10,000 in an account that earns 5.4% compounded annually. Use graphical approximation methods to determine how long it will take for his total investment in the two accounts to grow to $35,000. It will take approximately years for his total investment in the two accounts to grow to $35,000. (Type an integer or decimal rounded to one decimal place as needed.)