Part A: Dillon was investigating the time it takes him to enter the water after making the jump from the diving board. He began solving the equation by completing the square and arrived at the following form. -2(t+B)2 + 249/16 what is the value of B?
Part B: How much time does it take Dillon to enter water after the jump from the diving board? round answer to nearest tenth?
HELP ASAP

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.