What alkyl bromide(s) should be used in the malonic ester synthesis of each of the following carboxylic acids?

What alkyl bromide(s) should be used in the malonic ester synthesis of each of the following carboxylic acids?
a. propanoic acid,
b. 2-methylpropanoic acid,
c. 3-phenylpropanoic acid,
d. 4-methylpentanoic acid