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 hours. There were of the substance present at the beginning of the study. (a)Let be the time (in hours) since the beginning of the study, and let be the amount of the substance at time . Write a formula relating to . Use exact expressions to fill in the missing parts of the formula. Do not use approximations. (b)How much will be present in hours