Queen's Gambit Accepted, but Couldn't Capitalize [StartPly "8"]
[FEN ""]

1.d4 d5 2.c4 dxc4 3.e3 b5 4.a4 Ba6


White to move.

How to capitalize on this variation of Queen's Gambit Accepted for white? I've never seen this counter before.

Couldn't get pawn back and couldn't develop properly due to cramped queen-side.
You can play 5. axb5 and transpose to the answers to this question (Queen's Gambit Accepted with black trying to defend the c file pawn with 4... Bd7).