Consider the schema given in Question No$.13$ and write the relational algebra expressions for the following:

$($i$)$ Find all the patients who visits senior surgeon.

$(2)($in$)$ Find the patients $70$ years old or younger.

$(2)($lil$)$ Updatethe doctor's rank from surgeon to senior surgeonwho has $10$ years ofservice. $(2)$

$($iv$)$ Delete the patients who have not visited any surgeon.