A consumer watchdog organization takes a random sample of 500

A consumer watchdog organization takes a random sample of 500 bags of flour made by a company, weighs them, and discovers that 18 of them are underweight. Suppose that legal action can be taken if it can be demonstrated that the proportion of bags sold by the company that are underweight is more than 1 in 40. Would you advise the watchdog organization that there are grounds for legal action?