Answer
$P(Chris~or~Elaine)=\frac{2}{5}=0.4$
Work Step by Step
$N(S)=5$
$N(Chris)=1$
$N(Elaine)=1$
The events "Chris" and "Elaine" are mutually exclusive (disjoint).
Using the Addition Rule for Disjoint Events (page 270):
$P(Chris~or~Elaine)=P(Chris)+P(Elaine)=\frac{N(Chris)}{N(S)}+\frac{N(Elaine)}{N(S)}=\frac{1}{5}+\frac{1}{5}=\frac{2}{5}=0.4$
