The Temperature-Humidity Index I (Or Humidex, for Short) Is the Perceived

Short Answer

The temperature-humidity index I (or humidex, for short) is the perceived air temperature when the actual temperature is T and the relative humidity is h, so we can write I = f (T, h). The following table of values of I is an excerpt from a table compiled by the National Oceanic and Atmospheric Administration. For what value of T is $f ( T , 50 ) = 107$ ? $$\begin{array} { | c | c | c | c | c | c | c | } \hline \begin{array} { c } T&h \\\downarrow&\rightarrow\end{array} & 20 & 30 & 40 & 50 & 60 & 70 \\\hline 80 & 74 & 76 & 78 & 82 & 83 & 86 \\\hline 85 & 81 & 82 & 84 & 86 & 90 & 94 \\\hline 90 & 86 & 90 & 93 & 96 & 101 & 106 \\\hline 95 & 94 & 94 & 98 & 107 & 111 & 125 \\\hline 100 & 99 & 101 & 109 & 122 & 129 & 138 \\\hline\end{array}$$