You develop an app to help students complete their homework. To earn money, you sell advertising space on the app’s main screen. An advertiser pays you $25 per month and an additional $0.003 each time the app is opened.

Graph the linear equation that represents your monthly income y (in dollars) when the app is opened x times.

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.