The lengths of phone calls to the receptionist of a small company are i. i.d. with a mean of 5 minutes and an sd of 8 minutes. a) find or approximate the chance that the total length of the next 250 calls is less than 20 hours. b) did you use the normal curve in your calculation in a? if so, which of the following did the curve represent and why? pick one and explain. (i) the the distribution of the lengths of the next 250 calls (ii) the probability distribution of the total length of the next 250 calls (iii) the observed distribution of the total length of the next 250 calls