Generate binary trees for the following cases. In each case a set of records are

provided and these records $($containing the key value and the color of the node$)$ are

added sequentially to construct the binary tree. Once the tree is constructed, select

it if it is a valid red$-$black tree.

$\{(4,B),(2,R),(1,B),(5,R)\}$

$\{(40,B),(20,R),(45,R)\}$

$\{(50,B),(2,B),(56,R),(77,B),(80,B)\}$

$\{(50,B),(45,B),(53,B)\}.$