Why answer D is correct? It should be reported as a gain on the sale in the consolidated income statement because it is an inter company sale of land. I think A should be the right answer. Help me out please with explanation. Thank you

22) P C ompany purchased land from its 80% owned subsidiary at a cost of $30,000 greater than it subsidiary's book value. Two years later P sold the land to an outside entity for $15,000 more than P's cost. In its current year consolidated income statement P and its subsidiary should report a gain on the sale of land of: a) $15,000 b) $36,000