Using Data Envelopment Analysis (DEA) for an Inefficient Unit, a More

Using Data Envelopment Analysis (DEA) for an inefficient unit, a more efficient composite unit can be found by

A) Solving its DEA problem and retrieving the weights from the answer report.
B) Solving its DEA problem and examining those units whose final value is non-zero.
C) Solving its DEA problem and using the resulting shadow prices as composite weights.
D) Solving its DEA problem and using the positive resulting shadow prices as composite weights.