(c)
Given $P(A \cup B) = 0.6,\ P(A \cap B) = 0.3$
$\therefore\ P\left( A^{'} \right) + P(B^{'})$
$= 1 - P(A) + 1 - P(B) = 2 - \left\{ P(A) + P(B) \right\}$
$= 2 - \left\{ P(A \cup B) + P(A \cap B) \right\}$
$= 2 - \left\{ 0.6 + 0.3 \right\} = 2 - 0.9 = 1.1$