110 Points

GO

P(atleast one) = 1 – P(none)

P(1^{st} vendor not satisfying) = 1 – 0.8) =0.2

P(2nd vendor not satisfying) = 1 – 0.7) =0.3

P(3rd vendor not satisfying) = 1 – 0.5) =0.5

Therefore, P(none) = 0.2*0.3*0.5 = 0.03

Hence ans = 1 – 0.03 = 0.97