On 2 September 2020, Exclusive Antique Ltd. (EAL) posted a letter to Wonderful Hotel Ltd. (WHL) offering to sell WHL 10 antique chairs for HK$500,000. On 5 September 2020, WHL confirmed their acceptance by posted letter. However, the letter of acceptance never reached EAL and they subsequently sold the antique chairs to Great Hotel Ltd.

(a) Fully advise WHL whether or not their posted letter of acceptance is valid in contract law.

(b) Would you answer be different if the acceptance is made by email instead of by post? Explain your answer.