one MCQ relvent cost and decision making

Question

A farmer grows potatoes for sale to wholesalers and to individual customers. The farmer currently digs up the potatoes and sells them in 20 kg sacks. He is considering a decision to make a change to this current approach. He thinks that washing the potatoes and packaging them in 2 kg cartons might be more attractive to some of his individual customers. Which of the following is relevant to his decision?

(i) the sales value of the dug potatoes

(ii) the cost per kg of growing the potatoes

(iii) the cost of washing and packaging the potatoes

(iv) the sales value of the washed and packaged potatoes

(A) (ii), (iii) and (iv) only

(B) (i), (ii) and (iii) only

(C) (i), (ii) and (iv) only

(D) (i), (iii) and (iv) only

The answer is D . but can you explain why ??

Answer 1

Growing the  potatoes is irrelevant to the cost of bagging or bagging and washing them.  The added cost of washing the potatoes is key.