1)Seven blank spaces numbered 1 to 7, are arranged in a row in ascending from left to right.Two As',three Bs'and two Cs' are to be filled in these 7 blank spaces such no two (similar)alphabet occupy consecutive positions.In how many ways can this be done if B occupy the first place?

 

2)Three distinct numbers are randomly selected from first 20 natural numbers .Find the probability that these numbers are in a geometric progression?