Roberta is $11$ years old today. Suppose Helen deposits $$4000$ today,

and one year from today she deposits $$1000.$ Each year she increases

her deposit by $$500$ until she makes her last deposit on Roberta$$s

$18$th birthday. How much is on deposit after the $18$th birthday, and

what is the annual equivalent of her deposits? Contributed by Paul

R$.$ McCright, University of South Florida