What is the critical value equal to?

Studies seem to indicate that the average attention span has gradually decreased in the past 20 years with the rise of smartphones. In the early 2000s, the average attention span was mu equal to 640 seconds. A sample of n equal to 25 participants produced an average attention span of M equal to 360 seconds with s equal to 550 seconds. Based on this sample, has there been a significant decrease in the average attention span since the early 2000s? Use a significance level of 5%. What is the critical value equal to? O -2.069 O -2.064 O -1.714 O -1.711