A plot of land costing $200,000 was acquired on January 1, 2001. The price level was 120 on that date. One-quarter of the land was sold on December 31, 2001, for $60,000 when the general price level was 180. Compute the following holding gains:
a. Realized real holding gain.
b. Unrealized real holding gain.
c. Realized monetary holding gain.
d. Unrealized monetary holding gain.