Because of that, the pricing for business class on Acela Express is similar to that for reserved coach on other trains, with the main difference being that instead of the 4 fare levels and corresponding inventory codes/buckets, there are 5 fare levels and inventory codes on Acela Express business class.
Let's start by looking at a fare display from New York to Washington, DC, so you can see the hierarchy of fares. This is for travel on 23 December, the day before Christmas Eve (Christmas Eve Eve, if you prefer).
Starting from the top, the lowest fare is $142, fare basis DOAE, booked KD inventory, followed by the COAE at $166 booked in KC inventory, then $190 (KB inventory), $213 (KA inventory), and finally the full fare KOAE at $237 (K inventory). The ZOGE at $192 is also booked in K inventory but as the freeform information at right indicates, it is for government business travel.
So the hierarchy of inventory codes starts with KD at the lowest (like YD is lowest for reserved coach), then KC, then KB, then KA, and finally full-fare K. And in the New York-Washington, DC market, the ladder of fares go from $142 (KD), to $166 (KC), to $190 (KB), to $213 (KA), to $237 (K), depending on what is the lowest price available on a given train.
Now we'll look at business class availability for Acela Express trains from New York to Washington, DC, on the 23 December starting at 1 p.m.
Backward to # 13 - Fares, business class (non-Acela Express)
Forward to # 15 - Fares, first class (Acela Express)