On March 31, 2020, United Corporation acquired for $750,000 cash all the outstanding common stock of National Company when Nationals balance sheet showed total assets of $1,000,000 and total liabilities of $ 300,000. Out-of-pocket costs of the business combination may be disregarded. The current fair values of assets and liabilities of National were equal to their carrying amounts except for plant assets which was more than carrying amount by $ 50,000.The amount of goodwill is:

a.

$ 50,000.

b.

$ 0.

c.

$ 100,000.

d.

$ 150,000.