$A = ($a*($p1-$p2) + $b*($pT-$p1)/(-2));
$B = ($p1*($a*($p2-$p1) + $b*($pT-$p1)-$k*$d2-$d1i*$k));


##</code><code>##

 $A = -0.5*$b*($pT-$p1);
 $B = $b*($pT-$p1)-$k*($d2-$d1i);

##</code><code>##

$p2 = $p1; 
$p1 += .01;