Being a considerate father, I am planning a monetary incentive scheme to improve my 18-year-old son's marks at school. Instead of executing a relative's bequest as decreed, I intend to spend the €7,000 rewarding good results. During three semesters, he will have to pass 48 preliminary tests, then the main exams in the fourth and last semester. How should I divide up the capital?
Robert Saverin, a grateful father

Dear Mr Saverin,

Start by promising more than you can deliver. If you offer €10,000 for a perfect score, you will only need to apologise after your scheme has succeeded. That may seem to undermine your credibility, but the real risk lies the other way: your son may expect to get the money from his doting dad anyway. Discourage this view or your plan will be in vain.