a professional engineer who has in force a practising certificate issued under the Professional Engineers Act (Cap. 253) or any person under the direction or supervision of such a professional engineer; or
(b)
a corporation, partnership or limited liability partnership which is licensed under that Act to engage in professional engineering work in Singapore,
from carrying on any activity within the practice of professional engineering which he or it is authorised to carry on under that Act where to do so does not constitute a substantial part of services within the practice of architecture.