Mark Values His Drum Set at $800 and Ella Values

Multiple Choice

Mark values his drum set at $800 and Ella values her guitar at $1,000. Suppose that Mark trades his drum set for Ella's guitar.

A) This trade makes Ella worse off by $200.
B) This trade makes Mark better off by $200.
C) Mark must value Ella's guitar for at least $800, and Ella must value Mark's drum set for at least $1,000.
D) This trade decreases total value by moving the guitar and drum away from people who placed a high value on them.