Old Faithful is a geyser at Yellow Stone National Park. Two variables are measured on the geyser such that n = 20 (x, y) pairs were obtained. The two variables are:
1. Duration of an eruption (minutes).
2. TimeNext: Time until next eruption (minutes).
Below is the regression analysis from Minitab.

Coefficients
Term Coef SE Coef T-Value P-Value VIF
Constant 34.98 1.35 25.89 0.000
Duration 10.659 0.366 29.13 0.000 1.00

Model Summary
S R-sq R-sq(adj) R-sa(pred)
6.73929 78.82% 78.72% 78.46%

Regression Equation
TimeNext = 34.98 + 10.659 Duration

When considering all of the provided information which are true statements?

a) 78.82% of the variation in the time until the next eruption can be explained by the duration of an eruption
b) the degrees of freedom used with the slope test is 19
c) as a predictor, duration of an eruption is statistically significant
d) the parameter used with the slope test is b1