Yeah, I just said 20 for an easy round number that will also work if OP’s flight into DCA is late and they cross into Peak Fare territory on Friday.

Edit: although, hm yes i forgot it’s just one way on each trip. Even if they pay 6 to get to IAD, they only need two more dollars to get back on a weekend to DCA. OP if you are still reading, make it ten bucks.