Please help:

A production line at the jam factory is able to process between 400 and 855 jars of Triple Berry Jam per hour. Assume that the number of jars per hour is uniformly distributed. a. Calculate the mean and standard deviation of the number of jars processed per hour. Round final answers to 1 decimal place. [2 marks] b. What is the probability that in the next hour between 515 and 699 jars are processed? Round your answer to 3 significant digits. [2 marks]