A new iPhone is estimated to lose 25% of its value every six months after its purchase. How much is the value of an iPhone that costs $799 after someone has owned it for two years? (Round to the nearest cent. Two decimal places.) *

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.