Consider 20 DS0 circuits that are multiplexed onto 3 outgoing circuits. The mean arrival rate at each DS0 circuit is 1 call per hour during the busy hour; calls last, on average, 5 minutes. Assume Poisson arrivals, exponentially distributed call durations, and that customers who attempt a call when all circuits are busy are blocked (ignore call retry). The probability of blocked calls is: (Use 2 digits to the right of the decimal point.)