I would also be very surprised if the answer that the teacher is looking for is as convoluted as the one we have proposed.
There must be an element of 'send three and fourpence we are going to a dance' about this.

Teachers make mistakes, just like we all do.
They can't seriously be looking for this answer.

Is the question correct in its wording?
If not, the teacher needs sorting.
Especially if it is a she.

Its 42.

Hitchhikers Guide etc...
Answer to the Universe.

If I were the kid, I would point out that the work demands on the pipers are in clear and flagrant breach of the European Working Time Directive, and in solidarity with the workers it was against my principles to have anything to do with such a question.

A two and a half hour shift every 30 hours ?

Erm, twenty five hours