I think I found a bug #2

Using windows XP and xmaxima:

Plot2d is not working in  Maxima 5.9.1.9rc2

if I run the following batch file (named tank.mac)  it works (draws a 
graph) in 5.9.1  but not 5.9.1.9rc2.


kill(all);
globalsolve:true;
display2d:false;
solve([a1*s*h1=(h2-h1)/r1 + U, a2*s*h2= (h1-h2)/r1 - h2/r2],[h1,h2]);

h11:ev(h1 ,[a1=1,a2=1,r1=.5,r2=1/3], ratsimp);

h22:ev(h2 ,[a1=1,a2=1,r1=.5,r2=1/3],ratsimp);

y2:ev(h22,u=1/s);
ya(t):=ilt(y2,s,t)$
ya(t);

y1:ev(h11,u=1/s);
yb(t):=ilt(y1,s,t)$
yb(t);


plot2d ([ya(t),yb(t)],[t,0,6],[gnuplot_preamble, "set grid","set  xtics 
0,.1,6"]);
values;



Question #2
the output of values is
[h1,h2,h11,h22,y2,y1]
Why does ya(t) not show up?
and/or how do i see a list that would include ya(t)?

Thanks again for a great program. and for your help.

Doug Stewart