## WeBWorK Problems

### Re: FormulaWithUnits context error?

by Davide Cervone -
Number of replies: 0
Note that units are case sensitive, so mL is not the same as ml. The unit ml is defined, but mL is not, so in your expression
$ans11 = FormulaWithUnits("$an1 mg/mL");

the mg/mL is not recognized as a unit by FormulaWithUnits, and the expression is treated as a plain formula, in which mg and mL would be variables. But these aren't defined, so it reports that error.

If you switch to

$ans11 = FormulaWithUnits("$an1 mg/ml");

that should work.