A local trucking company fitted a regression to relate the cost of its shipments as a function of the distance traveled. The Excel fitted regression is shown. A scatter plot has a line graph which plots for distance in miles versus the shipping cost in dollars. An uptrend is depicted from $100 at 0 miles to $600 at 200 miles. The equation on the plot is y equals 2.8666x plus 104.55. Below is another equation; R power 2 equals 0.8478. How many degrees of freedom would we use to perform a t-test for zero slope H0: 1 = 0? Multiple Choice 22 20 18 21