Do Americans work more than the French? American adults work on average 43.5 hours per week with a standard deviation of 4.6 hours. French adults work an average of 36 hours per week with a standard deviation of 5.1 hours. A random sample of 110 Americans and 135 French adults were selected and surveyed about their work time. What is the probability that the sample mean for French is greater than that of the Americans?

With a probability of 0.85 the difference in average hours per week worked (American - French) is above what number?