The airline companies often change their flight prices over time. Assume Mary is planning her trip to New York City during the Christmas holiday. When she first checked the price in September, the ticket price was $300 round trip per person. However, when she checked the price again in early December, she noticed the price increased to $600 round trip per person for the same flight. This is an example of .

Sales at a fast-food restaurant average $6,000 per day. the restaurant decided to introduce an advertising campaign to increase daily sales. to determine the effectiveness of the advertising campaign, a sample of 49 days of sales were taken. they found that the average daily sales were $6,300 per day. from past history, the restaurant knew that its population standard deviation is about $1,000. if the level of significance is 0.01, have sales increased as a result of the advertising campaign? multiple choicea)fail to reject the null hypothesis. b)reject the null hypothesis and conclude the mean is higher than $6,000 per day. c)reject the null hypothesis and conclude the mean is lower than $6,000 per day. d)reject the null hypothesis and conclude that the mean is equal to $6,000 per day. expert answer