Which of the following is true for the sum of nnn independent Exponential(λ)\text{Exponential}(\lambda)Exponential(λ) variables?
It follows a Gamma(n,λ)\text{Gamma}(n, \lambda)Gamma(n,λ) distribution
It follows an Exponential(nλ)\text{Exponential}(n\lambda)Exponential(nλ) distribution
It follows a Poisson(nλ)\text{Poisson}(n\lambda)Poisson(nλ) distribution
It follows a Normal(n/λ,n/λ2)\text{Normal}(n/\lambda, n/\lambda^2)Normal(n/λ,n/λ2) distribution