Nick Andrewson uses gas to heat his home. He has accumulated the following information regarding his monthly gas bill and monthly heating degree$-$days. The heating degree$-$days value for a month is found by first subtracting the average temperature for each day from $65$ degrees and then summing these daily amounts together for the month.

Month Heating Degree$-$Days Gas Bill

February $850$ $$193\mathrm{.}50$

April $300$ $$78\mathrm{.}00$

What will be the increase in Nick$$s monthly gas bill per heating degree$-$day using the high$-$low method?