A thin, nonconducting rod of length L lies along the positive x-axis with its ends at x = 0 and x = L. The rod carries a non-uniform linear charge density given by \lambda(x) = \alpha x, where \alpha is a positive constant. Point P is located on the x-axis at x = L + d, a distance d from the right end of the rod. Which of the following integral expressions correctly gives the magnitude of the electric field at point P in terms of the given quantities and physical constants?