Aconsumer is trying to decide between two long-distance calling plans. the first one charges a flat rate of 10¢ per minute, whereas the second charges a flat rate of 99¢ for calls up to 20 minutes in duration and then 10¢ for each additional minute exceeding 20 (assume that the calls lasting a noninteger number of minutes are charged proportionately to a whole-minute's charge). suppose the consumer's distribution of call duration is exponential with parameter λ. (a) explain intuitively how the choice of calling plan should depend on what the expected call duration is.