One law for skin healing is A = A0e^-01t, where A is the number of square centimeters of unhealed area after 1 days and A0 is the
number of square centimeters of the original wound. If the original wound was 21 square centimeters, how many days will be needed for
the wound to reduce to 6 square centimeters? Round your answer to two decimal places.



Answer :