Question: MapleTA graphing algorithm

Hi all,

I am attempting to construct a randomized questions using algorithms and the sketch question type.

I have defined my variables algorithmically.  The sketch question type only allows a static answer, and hence I am trying to modify the code.  

As you can see below the code (part.1.answer...) is looking for points located at (7,0) and (0,-7).  I would like to replace the 7 with variable $xint and -7 with variable $yint, but it seems the @-symbols are some form of termination point that won't allow variables to carry-into the expression.

Looking for ideas??  I do not want to change to multiple choice.

Thanks,

mode=Inline@
id=0@
name=Graph a linear relation in Ax+By=C form@
comment=<p>&nbsp;</p>

@
editing=useHTML@
solution=@
algorithm=$b=range(1,6,2);
$c=range($b,20,$b);
$a=$b*3;
$zero=0;
$xint=$c/$a;
$yint=$c/$b;@
customCss=@
appliedThemes=@
uid=316f7dda-d8bc-479f-a3e4-9703a1846072@
privacy=10@
allowRepublish=false@
description=@
difficulty=0.0@
modifiedIn=11.10@
modifiedBy=a0c70480-e1aa-418d-9980-0347cddc1087@
school=7f01c0fb-116a-4f9d-bafc-e91de0b62105@
attributeAuthor=true@
numberOfAttempts=1@
numberOfAttemptsLeft=1@
numberOfTryAnother=0@
numberOfTryAnotherLeft=0@
question=<p><span style="font-size:16px;">Graph &nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow> <mn>$a</mn> <mspace width="5px"></mspace> <mi mathvariant="italic">x</mi> <mo>+</mo> <mi mathvariant="italic">&nbsp;</mi> <mn>$b</mn> <mspace width="5px"></mspace> <mi mathvariant="italic">y&nbsp;</mi> <mo>=</mo> <mn>$c</mn> </mrow></math>&nbsp; on the grid below.</span></p>

<p>&nbsp;</p>

<p><span>&nbsp;</span></p>

<1>

<p><span>&nbsp;</span>&nbsp;</p>

@
weighting=1@
numbering=alpha@
part.1.grid=true@
part.1.comment=<p>&nbsp;</p>

@
part.1.editing=useHTML@
part.1.attributeAuthor=false@
part.1.options="visible_buttons":"createline:1, delete"@
part.1.givenCurves={"sketchElements":[{"elementType":"topGroup","parents":[],"attributes":{"name":"Top-level Group"},"gradingOptions":{},"id":"topGroup"}]}@
part.1.modifiedIn=11.10@
part.1.numberOfAttempts=1@
part.1.allowRepublish=false@
part.1.numberOfTryAnotherLeft=0@
part.1.numberOfAttemptsLeft=1@
part.1.mode=Html5sketch@
part.1.numberOfTryAnother=0@
part.1.answer={"sketchElements":[{"elementType":"topGroup","parents":["jxgBoard1L160"],"attributes":{"name":"Top-level Group"},"gradingOptions":{},"id":"topGroup"},{"elementType":"point","parents":[7,0],"attributes":{"name":"B"},"gradingOptions":{},"id":"jxgBoard1P158"},{"elementType":"point","parents":[0,-7],"attributes":{"name":"C"},"gradingOptions":{},"id":"jxgBoard1P159"},{"elementType":"line","parents":["jxgBoard1P158","jxgBoard1P159"],"attributes":{"name":"aq"},"gradingOptions":{},"id":"jxgBoard1L160"}]}@
part.1.gradingCode=op(1,[Grading:-GradePlot($ANSWER, $RESPONSE, $PLOTVIEW)]);@
part.1.axes=-10,10,-10,10@
part.1.difficulty=0.0@
part.1.ticks=4,5,4,5@
part.1.name=responseNaN@