A certain brand of flat white interior latex paint claims one-coat coverage of 400 square feet per gallon. The standard deviation is known to be 20. A sample of 16 gallons is tested. (a) At α = .05 in a left-sided test, find the β risk and power assuming that the true mean is really 380 square feet per gallon. (b) Construct a left-sided power curve, using increments of 5 square feet (400, 395, 390, 385, 380).