In addition, the UN Model Convention embodies the idea that it would be appropriate for the country of residence to extend a double taxation exemption measure, either through foreign tax credits or exemptions, as in the OECD Model Convention. 3. For the purpose of determining the profit of a permanent establishment, expenses incurred for the purposes of the business of the establishment shall be allowed as a deduction, including an adequate apportionment of administrative and general costs, research and development costs, interest and other expenses incurred for the purposes of the enterprise as a whole (or that part thereof which includes the permanent establishment). which have arisen in the State in which the permanent establishment is situated or elsewhere, in accordance with the provisions and restrictions of the tax laws of that State. . . .