Probability Word Problem involving Inequalities

Leah is asked to get a red sleeping bag out of the back seat of her mother's car. There are 7 sleeping bags in the car, only 2 of which are red. All the bags are in black, zippered cases, so there is no way to tell which sleeping bag is which without opening the cases. Leah picks **s** cases, with **s** < 5, and discovers that not one of these cases contains a red sleeping bag. She tosses each of these cases into the front seat of the car. In terms of **s**, what is the probability that the next case Leah chooses from the back seat will contain a red sleeping bag?

I have never seen a probability problem like this before. It seems to me that the answer is 2/(2<*s*<7)?