Find the Indicated Probability $P ( A ) = 0.4 , P ( B ) = 0.5$

Find the indicated probability.
-If $P ( A ) = 0.4 , P ( B ) = 0.5$ , and $P ( A$ and $B ) = 0.3$ , find $P ( A$ or $B )$ .

A) $\mathrm { P } ( \mathrm { A }$ or $\mathrm { B } ) = 0.8$
B) $\mathrm { P } ( \mathrm { A }$ or $\mathrm { B } ) = 0.5$
C) $\mathrm { P } ( \mathrm { A }$ or $\mathrm { B } ) = 0.6$
D) $\mathrm { P } ( \mathrm { A }$ or $\mathrm { B } ) = 0.9$