Zed plc contracted to build an apartment block for Exe Ltd.

Zed plc contracted to build an apartment block for Exe Ltd. Which of the following would provide Zed with a valid excuse not to proceed with the contract?

(i) A key employee who was to manage the project has resigned.

(ii) The price of the materials to be used by Zed plc have increased to such an extent that the building can only be completed at a loss to Zed plc.

(iii) Planning permission has been refused.