Let \(f:[0,5] \to \mathbb{R}\) be such that \(f''(x) = f''(5-x)\), \(\forall\, x \in [0,5]\), \(f'(0) = 1\) and \(f'(5) = 7\), then the value of \(\displaystyle\int_1^4 f'(x)\, dx\) is:
Let d1 [(x1, y1), (x2, y2)] = |x1 - x2| + |y1 - y2| and d2 [(x1, y1), (x2, y2)] = \(\sqrt{\left(x_{1}-x_{2}\right)^{2}+\left(y_{1}-y_{2}\right)^{2}}\) denote the distance between (x1, y1) and (x2, y2) on the coordinate plane. The area of the region enclosed by the set of points (x, y) satisfying d1 [(x, y), (0, 0)] \(\geq\) 1 and d2 [(x, y), (0, 0)] \(\leq\) 1, is :