Answer
$P(postterm)=\frac{242,139}{4,305,340}=0.05624$
Work Step by Step
The sample space: $4,305,340$ babies born in 2007. So, $N(S)=4,305,340$
According to the marginal distribution (see page 235) of the third column: $N(postterm)=242,139$
Using the Empirical Approach (page 258):
$P(postterm)=\frac{N(postterm)}{N(S)}=\frac{242,139}{4,305,340}=0.05624$
