Answer and Explanation:
"Why do you or why don't you think this would encourage more customers to purchase from Woolworths?"
OR
"How do you think this would encourage more customers to purchase from Woolworths?"
Essentially when trying to turn "yes/no" questions into open-ended question, we want to change the "question word" (in this case, it's "do") into one that welcomes all sorts of answers. Examples of such new question words are "why", "how", "what", etc.
Here, since we're asking for the respondent's opinion of something, we probably want to use a "why" or a "how" question.
