VTMO 2017 — Grade 7 — final Question 2

$a ) A = 0.1 ( 2453$), with the parentheses denoting repetition. Find the least positive $k$ making kA integral. $b$)The six pairwise gcds of four distinct positive integers are $1 , 2 , 3 , 4 , 5 , N , N \gt 5$. Minimize $N$.