dS(t)/s(t)=dt+W2(t) iQ(2),Q(i)8d+8dW2(i) where W1 has ontation j with W2 corresponding probatilty Pr, where r ano rf are the U5 and the Euro rlak-tree interest rates: W1(l)=it+W1(l);W2(i)=jpt+W2(l) W1(t)=qt+W1(t);W2(t)=jttt+Wg(t) dS(t)/s(t)=dt+W2(t) iQ(2),Q(i)8d+8dW2(i) where W1 has ontation j with W2 corresponding probatilty Pr, where r ano rf are the U5 and the Euro rlak-tree interest rates: W1(l)=it+W1(l);W2(i)=jpt+W2(l) W1(t)=qt+W1(t);W2(t)=jttt+Wg(t)