This is the payment page for the May trip, linked off the main tour page: http://www.irishcenterwne.org/events/2019-spring-ireland-tour/2019-spring-tour-payment/ You can see the options for paying the balance for a double or single room. Click the one you need, and it will take you to PayPal, where you can pay with your credit card linked to your account (or set up an account if you need to).
I am not sure, please call the icc on Monday they can help you with that.
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