Dear Mayank

3 balls are selected without replacement if  no two of the selected balls have same colour then 

 = ^bC₁ * ^2bC₁ *^3bC₁ 

Probability P =[ ^bC₁ * ^2bC₁ *^3bC₁  ]/^6bC₃

                    =6b² /(6b-1)(6b-2)

 for P = 0.3

  6b² /(6b-1)(6b-2)  =0.3

  8b² -9b +1 =0

  b=1 and b =1/8

 b can not be 1/8

 so only one value of b =1

option b is correct

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