please help me with this homework problem. and please explain how to do it

2. Consider scanning literals for representing carbohydrates in chemistry. Such literals consist of one or more parts, each consisting of C, H, or O, optionally followed by a decimal integer greater than 1 (it can greater than 9). You may use Do to mean decimal digits 0-9, Di to mean 1-9, and D2 to mean 2-91 (a) Give a regular expression for these carbohydrate literals. You may use the iteration operators* and + and ?. (b) Give a DFA that recognizes exactly these literals (no e edges). Don't forget to mark the stant state and all accepting states Make sure that you don't accept the empty string