please answer the following ASAP

6	Use the following data for problems 6.a and 6.b. A community college instructor finds that his students score on an exam is normally distributed with a population mean = 83 and population standard deviation = 5.
6.a	The instructor wants to pass 95% of the class. What should be the minimum passing grade?
6.b	The instructor wants to give As to 30% of his students. What should be the minimum grade for an A?
7	For problem 7.a and 7.b, assume the following. A manufacturer of high intensity lamps finds that the useful life of the lamps is normally distributed with population mean = 70 months and population standard deviation s = 12 months.
7.a	A sample size n = 16 is taken. What is the probability that the sample mean is greater than 75 months?
7.b	The manufacturer wants to write a warranty so that only 1.5% (0.015) of the lamps fail while still under warranty. For how long should the warranty be written?
8	Assume that 84% of American teenagers attend a public high school. A random sample of 400 American teenagers is taken. What is the probability that 325 or fewer attend a public high school?
9	Using the normal table find z0.15, the value of z that gives an area of0.15 in each tail.