$title 'No mixed mode is allowed in equations' (COMPILE3,SEQ=321)

sets t, CityS(t);
Variables BuyNet(t),SellNet(t);
Equations  Bal1(t), bal2(t),bal3(t);

Bal1(t)..BuyNet(t)=e=citys(t)+sellnet(t);
$if errorfree $abort do not allow mixed mode in equs
$clearError

Bal2(t)..BuyNet(t)=e=citys(t);
$if errorfree $abort do not allow mixed mode in equs
$clearError

Bal3(t)..citys(t)=e= sellnet(t);
$if errorfree $abort do not allow mixed mode in equs
$clearError

$terminate