(with color reversed)
Just happened upon this old question (how much are a & b, IF a is gote...)
here is my take, but first I dont think a is gote...
1/ lets suppose it is :
123 is a classic 1 point gote miai value but we still need to add the value of the cut left at c when W tenuki. From Corner12ConnectionValue we know that c is worth 2 2/3
so a in gote (or b) would be worth 1 + (2 2/3)/2 = 2 1/3
2/ Is it gote ?
If a is worth 2 1/3, then it's worth less than c,
which means that it is the biggest gote left for W after (unless there was a mistake or this was used as a ko threat)
3/ So why was the initial hanetsugi gote in Corner12ConnectionValue then ? if I understand correctly, in that situation the initial hanetsugi was way bigger, because it was sente for W :