Given , Each node of order = 3 and each node can hold = 2 keys
Level 1 --- > No of keys = 2 No of children = 3
level 2 ----> No of keys = 3 x 2 No of children = 3x3
level 3----> No of keys = 3 x 2 x 2 No of children = 3 x 3 x 3
therefore , No of leaf node at max = 3 x 3 x 3 = 27
there're total 27 leaf nodes and each leaf node can hold 2 keys = 54 keys
Now , From the given diagram we can easily see that 9 keys are already present in the leaf node
therefore , Additional number of keys that can be inserted into B + tree = 54 - 9 = 45 keys