Show how you would prepare the following compounds starting from the given compound.

a$)2-$Butenoic acid from $2-$butenal

b$)$ trans$-3-$Pentenoic acid from trans$-1-$bromo$-2-$butene

c$)$ Benzyl bromide from phenylacetic acid

d$)$ Ethyl valerate from ethanol

e$)$ Phenylacetic acid from benzyl chloride