A murder has been committed. The only clue is a grocery receipt left at the scene by the murderer. The receipt shows that 2 kilos of tomatoes selling for $2 a kilo, 5 kilos of oranges selling for $1 a kilo and 3 kilos of mango selling for $3 a kilo were bought that day. There are two suspects: Bluebeard and Tinkerbell. On searching their apartments, you find each suspect's grocery bill for the previous week. Last week tomatoes were $3, oranges were $6 and mango was $5 a kilo. Bluebeard bought 1 kilo of tomatoes, 7 kilos of oranges and 2 kilos of mango at those prices. Tinkerbell bought 4 kilos of tomatoes, 4 kilos of oranges and 1 kilo of mango at those prices. Supposing that these people have well-behaved preferences, can you tell who is not the murderer?