Alone in Your Dim, Unheated Room You Light One Candle ${ } ^ { \circ } F$

Alone in your dim, unheated room you light one candle rather than curse the darkness.Disgusted by the mess, you walk directly away from the candle.The temperature (in ${ } ^ { \circ } F$ )and illumination (in % of one candle power)decrease as your distance (in feet)from the candle increases.The table below shows this information.
$\begin{array}{ccc}\text { distance(feet) } & \text { Temp. }(\mathbf{F}) & \begin{array}{c}\text { illuminatiou } \\(\%)\end{array} \\0 & 55 & 100 \\1 & 54.5 & 85 \\2 & 53.5 & 75 \\3 & 52 & 67 \\4 & 50 & 60 \\5 & 47 & 56 \\6 & 43.5 & 53\end{array}$ Suppose you know that at 6 feet the instantaneous rate of change of the illumination is -3.5 % candle power/ft.At 7 feet, the illumination is approximately _____ % candle power.