How old were the 500 arhats when they became arhats?

How old were each (or several) of the Buddha's students when they became arhats? I know Buddha was 35. I researched so far by Googling it and also by looking into Sariputra's life and also trying to infer based on what station in life that arhat was at. My question comes from the thought, "Hey, if a 37 year old can become an arhat, maybe I can too!" As a way to motivate and inspire myself.