Significance Test for Population Slope Least-Squares Regression Inference

This problem is from the following book: goo.gl/t9pfIj
This is part two for a least-squares regression inference. In part one, we checked the conditions for inference and created a 95% confidence interval to estimate the true slope of the population least-squares regression equation. Here is a link to that part:
In this part we conduct a significance test for population slope to see if there is statistically convincing evidence of a linear relationship between altitude and call duration (its a frog problem). We use a state, plan, do, conclude approach (the four-step solving process). We calculate a very low p-value and conclude there is a linear relationship between our explanatory and response variable. Next we connect our conclusion for this two-sided significance test to a confidence interval. Finally, we interpret s, r-square, and the standard error of the slope in context.