Linda invests $1000 in a savings account that pays a simple interest rate of 5% per year. At the same time, she invests another $1500 in a different account that pays a simple interest rate of 4% per year. If she wants to know how long it will take for the total interest earned from both accounts to reach $500, how many years will she have to wait? Let's think step by step and output the final answer within \boxed{}.
user