L.C.M of 40 = 5 x 8
Since 526ab is divisible by 5 and 8, b = 0
And since 526a0 is divisible by 8, the last three digits must be divisible by 8.
i.e. 6a0 must be divisible by 8.
because the last three digit of a number is divisible by 8 then the whole number is divisible by 8 .So here a=4 and b=0