Stamp duty shall not be charged in the case of a transaction that is effected by -
(a) a capital company which is formed for the purpose of and carries on exclusively the business of supplying a public service such as public transport or port facilities, or supplying water, gas or electricity, and not less than 50 per cent of the issued capital of which is owned by the State or a local authority, or
(b) a capital company whose objects are exclusively cultural, charitable or educational.