1273 Drainage Ditches (1)
1274 The Perfect Stall (1)
2112 Optimal Milking (4)
3041 Asteroids (5)
3308 Paratroopers (6)
2195 Going Home (6)
2516 Minimum Cost (7)
2455 Secret Milking Machine (7)
2226 Muddy Fields (7)
3281 Dining (7)
2391 Ombrophobic Bovines (8, challenge problem)
3498 March of the Penguins (8, challenge problem)