A generated exercise contains insufficient information but presents a precise solution. I propose that we check the consistency between demand, data and procedure before assigning it.
In the example, a necessary value is missing. The teacher can turn the error into an analysis activity, if he makes it explicit.
It should not leave students with the task of discovering an unexpected flaw and then evaluating them as incapacitated. Assistance in the preparation does not eliminate responsibility for the quality of the material.