Poissondistribution is a limitin case of binomial distribution...suppose X is a random variable....

P(X=k)=(^k)*e^-k/k!

where = is both the mean as well as the variance of X

 

cumin to the Q

here =5 and we require  P(X=1)+P(x=0)....sub in the above formula n we get the ans as 6/e⁵