P(X>=3)=P(X-μ >= 3-2.6) , μ=2.6 σ=0.4
=P(X-μ >=0.4) <= σ平方/(k平方+σ平方), k>0
→
P(X-μ >=0.4) <=0.2
乙林場不超過500*0.2=100棵符合條件