Carl is approaching the Canadian border on a trip from Vermont to Montreal, Canada, and the gas in his tank is low. He wants to determine if it would be more cost efficient to buy gas before or after crossing the border. He consults Gas Buddy and finds that the cost of gas in the US is $2\mathrm{.}73$ USD per gallon, while just across the border it is $$1\mathrm{.}40$ CAD per liter. The currency exchange rate is $$0\mathrm{.}750$ USD per $$1\mathrm{.}000$ CAD. How much more gas $($in gallons$)$ will he get for $$20$ USD if he buys the gas before crossing the border instead of buying it in Canada? $(1\mathrm{.}000$ liter $=0\mathrm{.}264$ US gallons$).$