Please explain in details, and I don't want answers copied from other WEBSITES ANSWERS. Thanks!

# 1

*Let T denote the time in minutes for a customer service representative to respond to 10 telephone inquiries. T is uniformly distributed on the interval with endpoints 8 minutes and 12 minutes. Let R. denote the average rate, in customers per minute, at which the representative responds to inquiries. Find the density function of R.In an exam taken by a large number of students, the scores (assumed to be continuous) have a normal distribution with mean 70 and variance 100. The examiners decide on the following scale: . [90, 100] - A . [80, 90) - B . [60, 80) - C . [50, 60) - D . [0, 50) - Fail Given that a randomly chosen student received a grade of C or higher, find the conditional probability that that student received a grade of B