A certain heat exchanger costs $30000 installed and has an estimated life of 6 years by the addition of certain auxiliary equipment when the heat exchanger is initially purchased,an annual saving of $1000 is operating cost can be obtained and the estimated life of the heat exchanger can be doubled. Neglecting any salvage value for either plan and with effective annual interest at 8%, what present expenditure can be justified for the auxiliary equipment? Use a study period of 12 years.