3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 58 61
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
I wrote the numbers down for 5 Sam sold and 3 David sold.
100 Sam sold, and David sold 61, although there's one more... It's something to start with.