In computation, the function f is defined by\(f\left( x \right) = \left\{ {\begin{array}{*{20}{c}} {a{x^2} + 2x - 1}&{x \le 1}\\ {b - c{x^2}}&{x > 1} \end{array}} \right.\)where a, b, c are constants. It is given that f(x) is differentiable at x = 1 and f'(0) = f'(2). Then the value of b is