(Reuters) -Netflix said on Tuesday its ad-supported tier had reached 70 million monthly active users globally, nearly doubling from about six months earlier as customers seek more affordable options. The plan, priced at $6.99 per month in the U.S., now accounts for more than half of all new Netflix (NASDAQ:) sign-ups in regions where it is available. It reached 40 million global monthly active users in May. Netflix’s cheapest plan