Can someone help me with these 3 questions please? I'm having an exam tomorrow it will really help. Thanks

The mean salary offered to students who are graduating from Coastal State University this year is $24,215, with a standard deviation of $3643. A random sample of 80 Coastal State students graduating this year has been selected. What is the probability that the mean salary offer for these 80 students is $23,750 or more? Carry your intermediate computations to at least four decimal places. Round your answer to at least three decimal places. 0 X 5 There is some evidence that, in the years 1981 - 85, a simple name change resulted in a short-term increase in the price of certain business firms' stocks (relative to the prices of similar stocks). (See D. Horsky and P. Swyngedouw, "Does it pay to change your company's name? A stock market perspective," Marketing Science v.6, pp. 320 - 35, 1987.) Suppose that, to test the profitability of name changes in the more recent market (the past five years), we analyze the stock prices of a large sample of corporations shortly after they changed names, and we find that the mean relative increase in stock price was about 0.85%, with a standard deviation of 0.12% Suppose that this mean and standard deviation apply to the population of all companies that changed names during the past five years. Complete the following statements about the distribution of relative increases in stock price for all companies that changed names during the past five years. (a) According to Chebyshev's theorem, at least 56% of the relative X ? increases in stock price lie between % and %. (Round your answer to 2 decimal places.) (b) According to Chebyshev's theorem, at least (Choose one) | of the relative increases in stock price lie between 0.61% and 1.09%. A manufacturing process produces semiconductor chips with a known failure rate of 6.8%. If a random sample of 215 chips is selected, approximate the probability that at least 16 will be defective. Use the normal approximation to the binomial with a correction for continuity. Round your answer to at least three decimal places. Do not round any intermediate steps. (If necessary, consult a list of formulas.) X 5