Cork City - Castleview, St. Lappan's Place Little Island

Hello,

Is there a simple way to go from Cork City to St. Lappan's Place Little Island?
I checked the directions on Google Maps and I have seen that there are two buses starting from the Cork City Bus Station [Parnell Place Bus Station]. They are the 240 and 260 buses.

I know full well that I may also take the train from Kent Station, but actually I wanted to get to the there by bus and without spending a lot of money.

How much would a return ticket cost by taking the 240 bus from Parnell Place Bus Station?

Thank you,
loveireland94