The general rule of thumb is to use a crossover cable betwen devices that are in the same layer of the OSI model and use a straight-through cable for devices that reside in different layers of the OSI model. For example, routers are in the layer 3 of the OSI model, so a router to router connection would require a crossover cable. Switches/Hubs are in the layer 2 of the OSI model, so switch to switch would require a crossover cable. Treat end user devices such as a PCs as layer 3 devices. So a PC (layer 3) to switch (layer 2) would require a straight through cable because they reside in different layers of the OSI model. If one of the devices is auto-sense then you don't have to worry about it and simply use a straight through cable.
In your scenerio, I would simple leave everything straight-through due to both devices are auto-sense. If they were not auto-sense, I would make (patch cable B) a crossover just because it seems to be at the main 'rack/patch panel' area of the network. I usually visually mark any crossover cables so the next person can easily identify what it is.
