The mean temperature in the layer between 750 hPa and 500 hPa decreases eastward by 3oC per 100 km. If the 750 hPa geostrophic wind is from southeast at 20 ms-1, what is the geostrophic wind speed and direction at 500 hPa? Let = 10-4s-1 and = 287 deg-1kg-1.