Mr. Chan owned a yacht and it was normally anchored at Sai Kung when he did not go sailing. Recently, Mr. Chan engaged Fever Limited to repair the engine of his yacht. Johnny, an employee of Fever Limited, was instructed by the company to replace some broken parts of the yacht's engine. Before the repairing work started, Johnny had been told by Mr. Chan to pay attention that some children used to swim around his yacht for fun and certain children had been accidentally injured before. Several days later, Johnny completed the repairing work and switched on the engine for testing purpose. However, he did not check around to see if there were any people swimming near the yacht in unsafe distance. Unfortunately, a child swam very close to the yacht at that moment and was seriously injured by the operating propellers.

Questions:

(a) Discuss whether Johnny is liable to the child's injury on the ground of tort of negligence. You are required to cite a relevant case to support your answer.

(b) Discuss whether Johnny's wrongful act was done within the course of employment with Fever Limited and whether the company is vicariously liable for his negligence.