This story illustrates a situation named Parrondo's paradox. As usual, the reader is invited to find him/herself a solution.

Q3': Show that by playing e.g. twice Birawa then twice Murk again and again, a customer has a positive expectation value.

More information, especially connections with one-dimensional Brownian motion and so-called "flashing ratchets", are available in the following papers:
G. P. Harmer & D. Abbott, Parrondo's Paradox,
T. Philips & A. Feldman, Parrondo's Paradox is not Paradoxical.