Historically, WoolWord’s supermarket has found it sells an average of 2517 grapes per day, with a standard deviation of 357 grapes per day. Consider that the number of grapes sold per day is normally distributed. Find the probability (to 4 decimal places) that:
a) the number of grapes sold on a particular day exceeds 2300
b) the probability that the average daily grape sales over a three month (i.e. 90 day) period is less than 2500 grapes or more than 3000 grapes per day.