Binary search trees:

$($a$)$ Draw the binary search tree that results from inserting $($in order$)$ each of the elements in the array

$[69142175313]$

$($b$)$ What is the order in which nodes are visited by a pre$-$order traversal?

$($c$)$ Is this a complete binary tree?

$($d$)$ If $6$ is erased, what node will replace it$?$