Suppose I am using several items of the same set, but of different level or quality. A concrete example are those sets which mix armor or weapons with jewelry and cannot therefore be fully upgraded to gold quality, like briarheart, willpower, footman, etc. In this case, the tooltips show different values while the items are in the inventory, but of course when they are equipped they give a single bonus.
How is this bonus computed? (average, minimum, maximum, majority, or something else, of the individual values?)