P(X=x)=(e-λ*λx)/x!,
λ=0.5.
a)P(X=1)=(e-0.5*0.51)/1!=0.30327,
P(X=2)=(e-0.5*0.52)/2!=0.07582,
P(X>2)=1-P(X=0)-P(X=1)-P(X=2)=1-(e-0.5*0.50)/0!-(e-0.5*0.51)/1!-(e-0.5*0.52)/2!=0.01439,
E(X)=50000*0.30327+100000*0.07582+200000*0.01439=25623.50,
b) E(X2)=500002*0.30327+1000002*0.07582+2000002*0.01439=2091975000,
Var(X)=σ2=E(X2)-(E(X))2=2091975000-(25623.50)2=143511247.75,
σ="\\sqrt{Var(X)}=37886.82".
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