Level curves for barometric pressure (in millibars) are shown for 6:00 a.m. on a day in November. A deep low with pressure 972 mb is moving over northeast Iowa. The distance along the red line from K (Kearney, Nebraska) to S (Sioux City, Iowa) is 300 km. 1012 1016 1008 1020 1024 1012 -1004 -1000- 996- -992- 988- 984 980 976 972 1008 What are the units of the directional derivative? O mb O mb/km2 O km/mb O mb/km O km Estimate the value of the directional derivative of the pressure function at Kearney in the direction of Sioux City. (Round your answer to two decimal places.)