How far away is the mountain that is highest among Mourne Mountains from the Irish Sea?
Mourne Mountains: The Mourne Mountains ( ; Irish: "na Beanna Boirche" ), also called the Mournes or Mountains of Mourne, are a granite mountain range in County Down in the south-east of Northern Ireland. Mourne Mountains:  The highest of these is Slieve Donard at 850 m .
i don't know