Assume we have a bettor that bets bet $b<script type="math/tex"> which is <script type="math/tex">1/5<script type="math/tex"> of his bankroll <script type="math/tex">f<script type="math/tex">, <script type="math/tex">(b=1/5?f)<script type="math/tex"> and always gets a return of <script type="math/tex">11/10<script type="math/tex"> on the bet. The return, <script type="math/tex">b?11/10<script type="math/tex"> is added to the bank roll <script type="math/tex">f<script type="math/tex">. A new bet <script type="math/tex">b<script type="math/tex">, once again derived from <script type="math/tex">f<script type="math/tex"> is bet again with another return of <script type="math/tex">b?11/10<script type="math/tex"> then added to <script type="math/tex">f<script type="math/tex">. How to model this function?$