GDOT wants to research whether or not to change the speed limit on 285. In a sample of 40 cars, the average speed was 72.4 mph with a standard deviation of 4.8 mph. Build a 90% confidence interval for the mean speed of cars on 285. What is the critical value?
A. 1.64
B. 1.72
C. 1.62
D. 1.685