It costs $12 to rent a zip car for one hour. let him represent how many hours you rent the car. a. write an expression to show how much it would cost to rent the car for her hours. expression: b. it costs a total of total of $84 to rent the car. write an equation to show what is going on. equation: c. how many hours did you rent the car? equation:

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.