Where to enforce penalty (NF) ???

[Zeke5]

45 seconds left in the game and A is leading by 1 point. 2nd & 3 from B's 40, A32 dives up the middle and is facemasked, but continues on for a touchdown. With 38 seconds left, A captain decides that it would be best to take the penalty and run the clock out instead of the TD and kick off (A had 2 failed 2 point conversions and their kick off team gave up 2 touchdowns already to the state's best returner).

A has the right to accept this penalty this year, but where do you assess the penalty from?