If the probability that the random variable X takes the value x is given by P(X=x)=k(x+1) 3^-x, x=0,1,2,3 …, where k is a constant, then P(X ≥ 3) is…

If the probability that the random variable $\displaystyle X$ takes the value $\displaystyle x$ is given by $\displaystyle P(X=x)=k(x+1) 3^{-x}, x=0,1,2,3 \ldots$, where $\displaystyle k$ is a constant, then $\displaystyle P(X \geq 3)$ is equal to