Answer
$\{\},\{D\},\{E\},\{J\},\{D,J\},\{D,E\},\{J,E\},\{D,J,E\}$
Work Step by Step
D=Dave, J=Joanne, E=Erica.
Hence the subsets: $\{\},\{D\},\{E\},\{J\},\{D,J\},\{D,E\},\{J,E\},\{D,J,E\}$
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