B+ tree is an extension of B tree. The major differences from B tree are (1) all leaf nodes are linked together in a doubly-linked list, and (2) data points are stored on the leaf nodes only; internal nodes only hold keys and act as routers to the correct leaf node; the left child is smaller than the key and the right child is larger or equal than that. Please find any/all violations of a B+ tree structure in the following diagram. Assume the tree node can at most contain 4 data points (keys).