Ivan is saving money to buy a computer with. he started with $225 in his savings account and the first week he added $75, the second week he added $200, the third week he unfortunately had to take out $50 and the fourth week he added $125. how much more money does he need to save if the computer costs $895?

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.