** Using WeBWorK **

I am having trouble incorporating units in the answer checker with PGML and could use some help troubleshooting. I read some posts at the PREP workshop forum on problem authoring and checked out some other examples in the PGML documentation. There seem to be several variations of syntax using "NumberWithUnits" and "FormulaWithUnits". Some use double quotes, some single, some a combination of no quotes and some quotes.

For example I have seen:
$Temp = NumberWithUnits(" 5 ft");

Also,

$Temp = NumberWithUnits("$g", "m/s");
# (where $g has been defined already)


WeBWorK doesnt like the following snippet and gets hung up on the lines that have NumberWithUnits or FormulaWithUnits. Ive tried a lot of variations by including or not including quotes around expresions.

Is there an easy fix?

-----------------------------------------------------------------------------

DOCUMENT();
loadMacros(
"PGstandard.pl",
"PGML.pl",
"MathObjects.pl",
"PGcourse.pl",
"parserNumberWithUnits.pl",
"parserFormulaWithUnits.pl",
"contextArbitraryString.pl",
"parserMultiAnswer.pl",
"parserPopUp.pl",
"contextInequalities.pl",
"PGgraphmacros.pl",
);
TEXT(beginproblem());
$showPartialCorrectAnswers = 1;

Context("Numeric") ;
Context()->flags->set(tolerance => 0.01);
Context()->variables->add(v => "Real");
Context()->variables->add(k => "Real");
Context()->variables->add(t => "Real");


$g = 9.8;
$mass = random(18, 40, 2);

$DE_UP = Formula("-$g - k*v**2/$mass ");
$DE_DWN = Formula("-$g + k*v**2/$mass ");

$Temp = Compute("-sqrt($g*$mass/k)");
Terminal = FormulaWithUnits($Temp, 'm/s');

$K = random(0.7,0.9,0.05);

$Temp2 = -sqrt($g*$mass/$K) ;
$Terminal2 = NumberWithUnits($Temp2,'m/s');


BEGIN_PGML
[``\frac{dv}{dt} = ``] [_______________________]{"$DE_UP"}

[`` \frac{dv}{dt} = ``][_______________________]{"$DE_DWN"}

[``\lim_{t\rightarrow \infty} v(t) = ``] [_______________________]{"$Terminal"}
[@ helpLink("units") @]*

[``\lim_{t\rightarrow \infty} v(t) = ``] [_______________________]{" $Terminal2"} [@ helpLink("units") @]*

END_PGML

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

ENDDOCUMENT();