9. •• In the troposphere (the lowest part of the atmosphere), the temperature decreases rather uniformly with altitude at a so-called “lapse” rate of about 6.5 °C/km. What are the temperatures

(a) near the top of the troposphere (which has an average thickness of 11 km) and

(b) outside a commercial aircraft flying at a cruising altitude of 34 000 ft? (Assume that the ground temperature is normal room temperature.)