The range of a discrete random variable $X$ is $\{1,2,3\}$ and the probabilities of its elements are given by $P(X=1)=3 k^3, P(X=2)=2 k^2$ and $P(X=3)=7-19 \mathrm{k}$. Then, $P(X=3)=$
- A
$\frac{2}{3}$
- B
$\frac{2}{9}$
- C
$\frac{1}{9}$
- D
$\frac{4}{9}$
✓ Correct answer: A
Want the full step-by-step reasoning?