Answer
We use table 1 to solve this problem. $W = f(T, 50)$ gives Wind Chill index at Temperature $T$ Celsius and wind speed $50km/hr$
Work Step by Step
$W = f(T, 50)$ gives Wind Chill index at Temperature $T$ Celsius and wind speed $50km/hr$
If wind chill index is $W$ then it feels as cold as $W$ Celsius when there is no wind.
For the temperature when $T=5C$, $W$ is $-1C$. As the temperature keeps decreasing the wind Chill Index keeps decreasing as well. The Index decreases by $7C$ for every $5C$ decrease in temperature.