Question

The wind chill index W is given by: W=13,12+0,6215T-11,37*(V^0,16)+0,3965T*(V^0,16) where T is the temperature in celsius and V is the wind speed in km/h. At some point in time we have T=-10 and V=36. At what rate should the wind calm when the temperature is decreasing by 1 degree per hour for W to remain constant?

Thank you