1.Mike and Crista rent a jet ski while on vacation. The rental cost is represented by the function c(h) = 20h + 50 where h is the number of hours of use and c(h) is the total cost for h hours of use. How much will the cost be if they use it for 4 hours?

Arandom sample of n = 25 observations is taken from a n(µ, σ ) population. a 95% confidence interval for µ was calculated to be (42.16, 57.84). the researcher feels that this interval is too wide. you want to reduce the interval to a width at most 12 units. a) for a confidence level of 95%, calculate the smallest sample size needed. b) for a sample size fixed at n = 25, calculate the largest confidence level 100(1 − α)% needed.