2. The scores on a competency test for 2nd-year high school students have a normal distribution with mean 400 and standard deviation 100. (a) What proportion of students score less than 550? (b) What proportion of students score between 550 and 650? Show your calculations in each case.1. The reaction time to a stimulus for a certain test has mean 2.5 and standard deviation 0.4 seconds. (a) Find the z-score for a reaction time of 2.7 seconds. (b) Find the z-score for a reaction time of 1.9 seconds. (c) One of the answers above is positive and the other one is negative. What does that tell you about the original reaction times? Explain briefly