Let P(w1)=λ then P(w2)=2λ...P(wn)=2n−1λ Assumk=1∞P(wk) =1⇒1−21λ=1⇒λ=21So, P(wn)=2n1 A={2k+3ℓ;k,ℓ∈N}={5,7,8,9,10...} B={wn:n∈A} B={w5,w7,w8,w9,w10,w11,...} A=N−{1,2,3,4,6} ∴P(B)=1−[P(w1)+P(w2)+P(w3)+P(w4)+P(w6)] =1−[21+41+81+161+641] =1−6432+16+8+4+1=643