Incorrect Validation in infoxtoPostdix selfcheck problem

[irunestone]

Error reported in course pythonds on page InfixPrefixandPostfixExpressions by user vemkiran [email protected]
In the last self check question that states "Modify the infixToPostfix function so that it can convert the following expression", the expression provides is "5 * 3 ** (4 - 2) ".

So the answer generated by the program is "5 3 4 2 - ** *"

But when I enter that answer and submit, it says incorrect. But when I replace ** with ^, it accepts it as a correct solution.