The wind-chill index is modeled by the function 

W = 13.12 + 0.6215T - 11.37v^0.16 + 0.3965Tv^0.16
where T is the temperature (in 8C) and v is the wind speed (in km/h). The wind speed is measured as 26 km/h, with a possible error of ±2 km/h, and the temperature is measured as ±11^oC, with a possible error of ±1^oC. Use differentials to estimate the maximum error in the calculated value of W due
to the measurement errors in T and v.