Atmospheric pressure P decreases as altitude h increases. At a temperature of 15oC, the pressure is 101.3

Question:

Atmospheric pressure P decreases as altitude h increases. At a temperature of 15oC, the pressure is 101.3 kilopascals (kPa) at sea level, 87.1 kPa at h = 1 km, and 74.9 kPa at h = 2 km. Use a linear approximation to estimate the atmospheric pressure at an altitude of 3 km.