随机变量X-N(u,σ2)则X在区间(u-σ,u+σ),(u-2σ,u+2σ),...

随机变量X-N(u,σ2)则X在区间(u-σ,u+σ),(u-2σ,u+2σ),(u-3σ,u+3σ)内的概率分别为68.3%,95.4%,99.7%.已知一批10000只的白炽灯泡的光通量服从N(209,6.52),则这样的10000只的灯泡的光通量在(209,222)内的个数大约为( )A.3415B.4770C.4985D.9540