A supermarket sells one particular item in its store on a regular basis. It currently has 750 units of this item in stock and no deliveries are expected until next week. The manager knows that average weekly sales of this item are 625, standard deviation of 55, and that sales are Normally distributed. Calculate the probability that the firm will not have enough stock to meet sales. How much stock should be kept if we want the chance of not having enough stock to be no more than 1 per cent?