$\displaystyle T_{wc} = 13.12 + 0.6212 \cdot T_a - 11.37 \cdot V^{0.16} + 0.3965 \cdot T_a \cdot V^{0.16}$

This is the wind chill formula, see Wind chill - Wikipedia, the free encyclopedia

T is temperature, V is the wind velocity.

Let T = -10 C centigrade at some time and V = 10 m/s. At what rate must V be reduced for W to remain constant when T is reduced by 1 C centigrade per hour?