(a)
Given ,$\ R = k\lbrack A\rbrack\lbrack B\rbrack^{2}$
Where [A]=[2A]and B=[2B]
$R' = k\lbrack 2A\rbrack\lbrack 2B\rbrack^{2}$
$= k\lbrack 2A\rbrack 4\lbrack B\rbrack^{2}$
$= 8k\lbrack A\rbrack\lbrack B\rbrack^{2}$
R’=8R
Thus, the rate will become eight times