How to determine the sampling distribution-single mean

QUESTION 1 The amount of sulfur in the daily emissions from a power plant has a normal distribution with a mean of 94 and standard deviation of 22. For a random sample of 5 days, find the probability that the average amount of sulfur emissions will exceed 80. QUESTION 2 According to the growth chart that doctors use as a reference, the heights of two-year-old boys are normally distributed with mean 34.5 inches and standard deviation 1.3 inches. If six two-year old boys are selected, what is the probability that their average height will be between 34.1 and 35.2 inches. QUESTION 3 The time spent using email per session is normally distributed with population mean of 8 minutes and standard deviation of 2 minutes. Random sample of 25 sessions is selected. Find the probability that the sample mean is between 7.8 and 8.2 minutes