I'm also confused by solutions to task 3 not being valid if "a painting is sent to a customer’s home, whereas this customer didn’t order it" considering that, from what I understand, paintings can't actually be sent directly to a customer's home anyway. I got the impression that you can se...

In Task 3, it says about L₄ and L₅ that "The first number will always be between 1 and N, and the second number will always be between 1 and C+P," yet in the example, L₄ contains numbers between 1 and C+P and L₅ contains numbers between 1 and N. Edit: Also, L₄ is used for two different thi...