Two mechanics worked on a car. the first mechanic worked for 10 hours, and the second mechanic worked for 15 hours. together they charged a total of $ 2500 . what was the rate charged per hour by each mechanic if the sum of the two rates was $ 205 per hour?

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.