Answer
$\{\},\{Joanne\},\{Erica\},\{Dave\},\{Erica,Joanne\},\{Dave,Joanne\},\{Dave,Erica\},\{Dave,Erica,Joanne\}.$
Work Step by Step
A subset A of a set B is a set A such that all elements of A are also in B.
Hence, here the the subsets:
$\{\},\{Joanne\},\{Erica\},\{Dave\},\{Erica,Joanne\},\{Dave,Joanne\},\{Dave,Erica\},\{Dave,Erica,Joanne\}.$