You expect your newly born child to attend college in 18 years. You have $12,000 to set aside for that purpose.

You expect your newly born child to attend college in 18 years. You have $12,000 to set aside for that purpose.
You also expect that the total cost of college education to be $100,000 by that time.

Calculate the interest rate at which you have to invest today to achieve your goal. SHOW CALCULATIONS AND WHAT NUMBERS GO INTO THE FORMULA.