>>5521502Child B, as the provider and self employed manufacturer of the flute is its natural owner.
But that doesn't mean she should have it, in the ideal society she should be able to sell her flutes on the open market, where the people who would benefit most from them could pick them up. By doing this child A gets the flute as well, either because she bought it herself, or an organization that collects and trains musical talent gave it to her as part of a work contract.
But this doesn't mean only child A will get to enjoy the flute, any good society recognizes the need for cultureral unity. As a result child A or her manager should be contracted by the government to perform on certain holiday, or other special events. Because these are for the cultural good of society everyone, even poor child C, can experience them for practically free. This will not only bring joy to his life, but also provide a sense of cultural unity discouraging criminal behavior.
So op the answer is like always, all of them
