For each of the compounds described by the following names,
1. draw a three-dimensional representation.
2. star (*) each chiral center.
3. draw any planes of symmetry.
4. draw any enantiomer.
5. draw any diastereomers.
6. label each structure you have drawn as chiral or achiral.
a. (S)-2-chlorobutane
b. (R)-1,1,2-trimethylcyclohexane