For the purpose of calculating entitlement to any benefit under the legislation of Ireland in accordance with Articles 14 to 29, any earnings factor achieved in any income tax year commencing on or after 6 April 1975 under the legislation of Great Britain, Northern Ireland or the Isle of Man shall be converted by the competent authority of the United Kingdom to contribution weeks under the legislation of Ireland by dividing the earnings factor by that income tax year’s lower earnings limit. The result shall be expressed as a whole number, any remaining fraction being ignored. The number of contribution weeks so calculated, subject to a maximum of the number of weeks during which the person was subject to the legislation of Great Britain, Northern Ireland or the Isle of Man, as the case may be, in that year, shall be treated as if they were contribution weeks completed under the legislation of Ireland.