9. A hot air balloonist is interested in the relationship between the number of times he engages the blast valve per minute (y) and the temperature inside the envelope of the balloon. Based on the collected data, the least squares regression line is = 3.41x + 10.53, where x is the number of degrees by which the temperature exceeds 45 C (113 F). Which of the following best describes the meaning of the slope of the least squares regression line?

a. For each increase in temperature of 1 C, the estimated number of times the bal- loonist engages the blast valve per minute increases by 10.53.

b. For each increase in temperature of 1 C, the estimated number of times the bal- loonist engages the blast valve per minute increases by 3.41.

c. For each increase in the number of times the balloonist engages the blast valve per minute, there is an estimated increase in temperature of 10.53 C.

d. For each increase in the number of times the balloonist engages the blast valve per minute, there is an estimated increase in temperature of 3.41 C.