Albert E$.,$ a bright elementary school kid and future entrepreneur, is thinking about his lemonade stand at Walmart. In the afternoon at $2$ pm his sales of cups of lemonade are falling at $13$ per hour. So he decides to raise his price at a rate of $$0\mathrm{.}05$ per hour to compensate. If he has sold $66$ cups at $2$pm and his price is $$0\mathrm{.}7$ per cup how fast is his revenue changing at $2$pm given his new pricing strategy. $($assume the changing price doesn't effect quantity sold$)$