“fair market value”, means –
(a) the price which could be obtained upon a sale of the property between a willing buyer and a willing seller dealing at arm’s length in an open market; or
(b) in relation to immovable property on which a bona fide farming undertaking is being carried on in the Republic, the amount determined by reducing the price which could be obtained upon a sale of the property between a willing buyer and a willing seller dealing at arm’s length in an open market by 30 per cent;