Port Blair, the capital city of Andaman and Nicobar Islands is directly connected to Chennai and Vishakapatnam via ship route. The ships sail from Chennai/Vishakapatnam to Port Blair and vice versa.
Swaraj Dweep and Shaheed Dweep are two popular tourist islands in Andaman Islands. One has to take a ferry from Port Blair to reach these islands. There are ferries that sail frequently between the three islands - Port Blair (PB), Swaraj Dweep (SwD) and Shaheed Dweep (ShD).
Shown below is a schematic representation of the ship routes and ferry routes.

(Note: The image is for representation purpose only.)
X is the set of all 5 places and Y is the set of 3 places in Andaman Islands.
That is, X = {C, V, PB, SwD, ShD} and Y = {PB, SwD, ShD}.
A relation R defined on the set X is given by, `R = {(?_1, ?_2):` there is a direct ship or direct ferry from ?_1 to ?_2}.
A function `?: Y rightarrow X` is defined by, `?(??) = ?, ?(???) = ??, ?(?ℎ?) = ???`
Check whether the function f is one-one and onto. Give valid reasons.