function getProb(n)
    results = zeros(n)
    for i in 1:n
        y = 3*rand()
        while true
            # k
            k = Int(floor(2*rand()))
            if k == 1
                break
            end
            y += 3*rand()
        end
        results[i] = y
    end
    return (mean(results),var(results))
end

μ,σ² = getProb(10000000)