estimation is as following:<br/>
<br/>
y*=x'b+e, e follows N(0,sigma^2) , normal distribution<br/>
<br/>
y*<a1   y<0 <br/>
<br/>
a1=<y*=<a2   y=0 <br/>
<br/>
y*<a2   y>0 <br/>
<br/>
How could I get the Ln[G(yj |  Xj,a,b)] in order to implement the Maximum Lilelyhood estimation<br/>
for a1 and a2?<br/>
<br/>
Could anyone please help me ?<br/>