Contract assent and content

Question

which one of the following methods is not an effective way to determine the price in a contract in which the details are incomplete?
A. A clause stating it to be 'on usual hire purchase terms'
B. Price to be at that ruling in the market on the day of delivery
C. An arbitrator to set the price
D. Price to be set by course of dealing between the parties

要講中文解釋
點解那個答案

Answer 1

A.
A clause stating it to be 'on usual hire purchase terms'
因為用 fhire purchase不是一種sales contract
there is no agreement to sell goods here

but the hirer does have an option to buy the goods.