I have a simple ODE problem as follows

##################################################

DOCUMENT(); # This should be the first executable line in the problem.

loadMacros(

"PG.pl",

"PGbasicmacros.pl",

"PGchoicemacros.pl",

"PGanswermacros.pl",

"PGgraphmacros.pl",

"PGmatrixmacros.pl",

"PGnumericalmacros.pl",

"PGauxiliaryFunctions.pl",

"PGmorematrixmacros.pl"

);

TEXT(beginproblem());

$showPartialCorrectAnswers = 1;

$a = random(2,9,1)*random(-1,1,2);

$b = - $a;

$y1 = non_zero_random(-9,9,1);

BEGIN_TEXT

Find the solution of the equation

\[ x y' + y = $b x y^2, \]

$BR

which satisfies \(y(1)=$y1.\)

$BR

$BR

\( y(x) = \) \{ ans_rule(50)\}.

END_TEXT

ANS(fun_cmp("1/($a*x*ln(x)+x/$y1)"));

ENDDOCUMENT();

######################################33

The problem works all right, but on the WW web page the following error message occurs:

#################################################

Checking additional error messages

pg debug---- main /opt/webwork/pg/macros/PG.pl 145 ------

No increment done. Using PG to inc_ans_rule_count =

WeBWorK::PG::Translator

/opt/webwork/pg/lib/WeBWorK/PG/Translator.pm

1621

(eval)

0

0

package main; ans_rule(50);

256

UUUUUUUUUUUU

#####################################################

What does this mean, and how do I get rid of it?

TIA,

-sen