Atmospheric pressure $P$ decreases as altitude $h$ increases. At a temperature of $15^\circ C$, the pressure is $101.3$ kPa at sea level, $87.1$ kPa at $h=1$ km, and $74.9$ kPa at $h=2$ km. Use linear approximation to estimate the atmospheric pressure at an altitude of $3$ km (use secant slopes as an approximation for the derivative).

kPa