A Particular Type of Radioactive Medical Waste Is Shipped to a "Cooling-Down

Short Answer

A particular type of radioactive medical waste is shipped to a "cooling-down" facility in sealed plastic barrels where it is housed until the radiation intensity falls below a fixed threshold. Upon arrival, a barrel contains 6 pounds of the radioactive material and must be stored until the radioactive component has decayed to 1 pound or less, after which time the barrel may be shipped out for final disposal. If the amount of radioactive waste in a barrel is given by the formula $A = 6 e ^ { - 0.02 t }$ where t is the number of days after arrival, how long must a barrel be stored before it can be shipped for final disposal? Round to the nearest tenth of a day.