Paint used to paint lines on roads must reflect enough light to be clearly visible at night. Let denote the mean reflectometer reading for

Paint used to paint lines on roads must reflect enough light to be clearly visible at night. Let µ denote the mean reflectometer reading for a new type of paint under consideration. A test of H0: µ = 20 versus Ha: µ > 20 based on a sample of 15 observations gave t = 3.2. What conclusion is appropriate at each of the following significance levels?
a. a = .05
b. a = .01
c. a = .001