In the following compound, identify all groups that would be considered substituents and then indicate the systematic name as well as the common name:
a) Methyl and ethyl; 2,2-dimethylpropane, isobutane
b) Methyl and propyl; 2,2-dimethylbutane, isopentane
c) Ethyl and propyl; 2,3-dimethylbutane, neopentane
d) Methyl and ethyl; 2,3-dimethylpropane, neobutane
