thank you in advance :)
There are 60 paths from A to B.
The corner approach: https://drive.google.com/file/d/1_8ND-xHAqQUfnQiimEe09dafdEiixI0C/view?usp=sharing
$B = 78 + 78 = \boxed{156}$
https://web2.0calc.com/questions/help_42168
=^._.^=