Air pressure decreases at a rate of 2 pascals per kilometer in the eastward direction. In addition, the air pressure is dropping at a constant rate with respect to time everywhere. A ship sailing eastward at 10 km/hr past an island takes barometer readings and records a drop of 50 pascals in 2 hours. Estimate the time rate of change of air pressure.

I think I should take the -2 pascals/km and multiply it by 10 km/hr and then add -50 pascals/2hr times 1 since there is a constant change with respect to time. So, I get - 45 pascals/hour. Can someone tell me if I am right? Thank you.