Lesedi and Simphiwe registered Furnmax $($Pty$)$ Ltd$,$ a company that sells office equipment. The Memorandum of Incorporation of Furnmax $($Pty$)$ Ltd indicates that the board of directors, consisting of Lesedi, Simphiwe, Carol and Precious, can appoint a managing director who would be authorised to contract on the company$$s behalf. However, the board has never formally appointed a managing director. Nevertheless, Lesedi, with the full knowledge of the other directors, has contracted with Office Supplies Ltd for the supply of office equipment to Furnmax $($Pty$)$ Ltd on two occasions. On the third occasion that Lesedi contracted with Office Supplies Ltd$,$ Furnmax $($Pty$)$ Ltd denied liability for the payment for the equipment based on the fact that Lesedi was never appointed as the managing director. Upon being sued by

Office Supplies Ltd$,$ Furnmax $($Pty$)$ Ltd opposed the claim for payment in terms of the agreement based on the fact that Lesedi was not authorised to contract on the company$$s behalf.

Explain with reference to relevant case law and section in the legislation what Office Supplies Ltd would have to prove in order to rely upon the doctrine of estoppel.