The mass of a substance, which follows a continuous exponential growth model, is being studied in a lab. The doubling time for this substance was observed to be 7 minutes. There were 63.3 mg of the substance present at the beginning of the study. (a) Let be the time (in minutes) since the beginning of the study, and let y be the amount of the substance at time t Write a formula relating y to f Use exact expressions to fill in the missing parts of the formula. Do not use approximations. y = De Dr 믐ing (b) How much will be present in 19 minutes? Do not round any intermediate computations, and round your answer to the nearest tenth. mg Expe