Pls, help me, I don't know how to do this A water tank in the shape of a cuboid is 16 cm long, 15 cm wide, and 40 cm high. the depth of the water in the tank was 27 cm originally. Ivan puts some stones into the tank. if the volume of each stone is 250cm3, at least how many stones should be put into the tank so the water will overflow?

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.