7. For a school fundraiser, Elena will make T-shirts. She will order T-shirts and print graphics on them. Elena must spend $349 on a printing machine and $4.80 per shirt for the blank shirts, ink, and other supplies.

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.