If two integers are chosen at random,what is the probability that their product is an even integer?

Let $A$ and $B$ be events with $P(A)=\frac{1}{3}, P(B)=\frac{1}{4}$ and $P(A \cup B)=\frac{1}{2}$. Then which of the following statements is incorrect?

The probabilities of an anti-aircraft gun shooting down an enemy plane in the first,second,and third shots are $0.6, 0.7$,and $0.1$ respectively. What is the probability that the gun shoots down the plane?

The probability of at least one of the events $A$ and $B$ occurring is $0.6$. If the probability of both $A$ and $B$ occurring simultaneously is $0.3$,then $P(A') + P(B') = \dots$

Four persons independently solve a certain problem correctly with probabilities $\frac{1}{2}, \frac{3}{4}, \frac{1}{4}, \frac{1}{8}$. Then the probability that the problem is solved correctly by at least one of them is

$A$ letter is chosen at random from the word $ASSASSINATION$. Find the probability that the letter is a consonant. (in $/13$)