It was a rough week for Rite Aid (NYSE: RAD) investors. Shares of the drugstore operator plummeted 15.4% last week, after the proposed purchase of the chain by Walgreens Boots Alliance (NASDAQ: WBA) ran into some resistance.Bloomberg reported that the Federal Trade Commission was considering filing a lawsuit that could derail Walgreens' pending $7 billion deal for Rite Aid, citing the Capitol Forum trade publication as its source.