6.56 Rate data often follow a lognormal distribution. Average power usage (dB per hour) for a particular company is studied and is known to have a lognormal distribution with parameters / = 4 and o = 2. What is the probability that the company uses more than 270 dB during any particular hour?6.57 For Exercise 6.56, what is the mean power usage average dB per hour)? What is the variance