3.08.02. Fees are considered fair and reasonable when they are justified by the circumstances and correspond to the services rendered. In determining his fees, the engineer must, in particular, take the following factors into account:
(a) the time devoted to the carrying out of the mandate;
(b) the difficulty and magnitude of the mandate;
(c) the performance of unusual services or services requiring exceptional competence or speed;
(d) the responsibility assumed.