: $$d_{x}\left( {t + \Delta t} \right) = {\max\limits_{\ }\left\{ {0,d_{x}(t) + b + g\left( {v_{x}(t) - i_{v}{\sum_{y \neq x}{v_{y}\left( t \right)}}} \right) + {N\left( {0,\sigma^{0}} \right)}_{x}(t)} \right\}}$$  For two alternatives, the 