You and a friend sign up for a health club. it costs $50 to join, plus $20 a month. however, the first 100 customers can sign up for $30, plus $20 a month. your friend is customer 100, and you are 101. if the accumulated cost for each membership were graphed, what would it look like? what would the difference be between your accumulated cost and your friend's accumulated cost at any given month?

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.