Marc's home is 10 blocks from the library. after school, marc walked from his house to his friends house, which is in the opposite direction of the library, at a rate of one block every two minutes. it took mark four minutes to walk to his friends house. after he met up with his friend, he immediately began to walk towards the library at a rate of one block everyone minute

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.