Answer:
Cost relevant or irrelevant for decision making to sell or process further
a. $15,000 already incurred is not relevant because this is sunk cost. This cannot be avoided or changed.
b. $20,000 selling price is relevant for decision making because this incremental revenue is generated if goods are sold semi-finished.
c. $22,000 additional selling price is for decision making because this cost is required for further processing and shall be incurred.
d. $35,000 revenue from processing is relevant for decision making because this incremental revenue is generated if goods are after further processing.