Atoy manufacturer has designed a new piece for use in building models it is a cube with side length of 7mm and it has a 3mm diameter circular hole cut through the middle the manufacture wants 1,000,000 proto types how much plastic is used for each prototype?

a- 343mm^3
b- 145mm^3
c- 29.50mm^3
d-293.5mm^3

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.