P(2≤X≤4)
=P(X≤4)-P(X≤2)
=Φ[(4-2)/σ]-Φ[(2-2)/σ]
=Φ(2/σ)-Φ(0)
=Φ(2/σ)-0.5
得Φ(2/σ)=P(2≤X≤4)+0.5=0.4+0.5=0.9
P(X≤0)
=Φ[(0-2)/σ]
=Φ(-2/σ)
=1-Φ(2/σ)
=1-0.9
=0.1
答案：0.1