man has $ 10,000 to invest. He invests $ 4000 at 5 % and $ 3500 at 4 %. In order to have a yearly income of $ 500, he must invest the remainder at:
(a) 6 %,(b) 6.1 %, (c) 6.2 %, (d) 6.3 %, (e) 6.4 %