17. LAWN SERVICE Trey estimates he will earn $470 next summer cutting lawns in his neighborhood. This amount is 2.5 times the amount a he earned this summer. Write and solve a multiplication equation to find how much Trey earned this summer. (Lesson 2B)

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.