VTMO 2026 - Grade 4 - Semifinal - SET 6 - Self-study Question 23

At a bookshop, each book bought earns one symbol from T, O, A, N. Collecting 5 T symbols, or 4 O symbols, or 3 A symbols, or 2 N symbols earns a gift. What is the smallest number of books one must buy to be certain of receiving a gift?