certain substance decomposes according to a continuous exponential decay model. To begin an experiment, the initial amount of the substance is 320 kg. fter 5 hours, 240 kg of the substance is left. (a) Let t be the time (in hours) since the beginning of the experiment, and let y be the amount of the substance (in kg) at time f. Write a formula relating y tot. Use exact expressions to fill in the missing parts of the formula. Do not use approximations. y =D: X G (b) How much of the substance is left 23 hours after the beginning of the experiment? Do not round any intermediate computations, and round your answer to the nearest whole number. kg