A company produces packets of biscuits with mean weight 125.0 grams and standard deviation 4.0 grams. Each time a consignment of biscuits is sent to a supermarket chain, a sample of 100 packets of biscuits are weighed. If the sample mean is less than 124 grams then the supermarket returns the entire consignment of biscuits to the producer. What is the probability that a consignment will be returned?