Andy gets a cavity for every 4 candy canes he eats. He gets 2 candy canes from his parents and 3 candy canes each from 4 teachers. Then he uses his allowance to buy 1/7 as many candy canes as he was given. How many cavities does he get from eating all his candy canes?
Please reason step by step, and put your final answer within \boxed{}.
user