A restaurateur asks if there is a linear relationship between the time (x) that a customer spends in their establishment and the amount to which the invoice is (y). After observing 35 clients, he noted the following statistical indicators:

x = 50 minutes, sx = 12 minutes, y = $ 35, sy = $ 9, sxy = 27

From these data, we wonder if the linear relationship observed between the time spent in a restaurant by a customer and the amount of his bill is significant. If the test level is 5%, determine the appropriate test statistic (Z) and conclude with C1 or C2, where:

C1: we can confidently conclude that there is a linear relationship between time and amount

C2: we cannot confidently conclude that there is a linear relationship between time and amount