A shipment of 10 Ford Pintos contains four that will explode if the rear bumper is struck by another car. In how many ways can a used car dealer purchase three of the Pintos and receive: a) three good cars
b) two good cars
c) at least one good car

In the diagram, points d and e are marked by drawing arcs of equal size centered at b such that the arcs intersect ba and bc. then, intersecting arcs of equal size are drawn centered at points d and e. point p is located at the intersection of these arcs. based on this construction, m , and m