44. Custom and usage.

An agent also has implied authority to act in accordance with the customs and usages of the place where1, or the business in respect of which2, his express authority permits him to act, subject to the condition that such customs and usages must not be unreasonable, or change the essential nature of the contract of agency3. Where the agent is a professional person, a contract made in the ordinary course of his profession and as agent is deemed to incorporate all reasonable4 usages, rules and regulations of that profession5.

To be recognised as such, a usage must be certain (meaning,