(a) The classification of costs as controllable and non-controllable depends upon a point of reference. Explain. (b) Direct costs and controllable costs are not necessarily the same. Comment. (c) Why...

(a) The classification of costs as controllable and non-controllable depends upon a point of reference. Explain.

(b) Direct costs and controllable costs are not necessarily the same. Comment.

(c) Why are sunk costs not relevant in decision-making?