Plan the workshop

You will model the workshop of the first lesson in code and search all the whole-number plans for the best one. The checker tests your functions on many plans.

The idea. A plan is a pair $(x, y)$ of tables and chairs. Cutting takes $2x + 3y$ hours, which must be at most $24$. Finishing takes $2x + y$ hours, which must be at most $16$. The profit is $50x + 40y$ pounds.

Your tasks.

1. Finish profit(x, y). Return the profit in pounds.
2. Finish is_allowed(x, y). Return True if $x \ge 0$, $y \ge 0$, and both hour limits are kept.
3. Finish best_plan(). Try every whole number $x$ and $y$ from 0 to 20, and return (best profit, x, y).