The number of bacteria in a flask grows according to the differential equation dy = 0.15y dt In this question, time is measured in hours and the number of bacteria, y, is measured in millions. The number of bacteria at time t = 0 is 25 million. a. Enter a formula for the number of bacteria at time t y = b. What is the value of the growth constant? Growth constant : per hour. c. How long does it take for the number of bacteria to double? (Enter your answer correct to two decimal places.) Doubling time : hours. d. How many million bacteria will be present after 4 hours have passed? (Enter your answer correct to one decimal place.) Number present after 4 hours: million.