Parents need to save for their children's education. Current costs of a year's tuition and living expenses are $20,000. The average degree is four years long. The average interest rate that the couple can get on their investments is 7%, and college fees are expected to rise by 7% per annum over the period. If the child has just been born, and college education will begin when the child is eighteen, how much money must the couple save each year to meet this expense?