For 115 consecutive days, a process engineer has measured the temperature of champagne bottles as they are made ready for serving. Each day, she took a sample of 10 bottles. The average across all 1150 bottles (115 days, 10 bottles per day) was 40 degrees Fahrenheit. The standard deviation across all bottles was 0.5 degrees Fahrenheit.

When constructing an X-bar chart, what would be the center line? Fahrenheit