A red$-$black tree $($RBT$)T$ is shown in the following figure, where the

nil nodes are not shown.

Suppose that we want to insert $28$ into the red$-$black tree in the

figure.

Let the new node be pointed to by P$.$ We need to perform insertion

fixup when necessary, so that the resulting tree is still a red$-$black

tree. In the resulting red$-$black tree, what is the left child of P$?$