private int GetNumInstancesOfOffer(List<Item> basket, Offer offer) { return (basket.Count(i => i.Name == offer.EligibleItem))/(offer.Quantity); }
private static double CalculateDiscount(IEnumerable<Item> items, Offer offer) => items .Where(i => i.Id == offer.ItemId) .Aggregate(0.0, (total, item) => item.Quantity + total) .CalculateDiscount(offer.DiscountQualificationQuantity, offer.Discount);