(a) Find ExXa/, where ExXa is given by (16.61). (b) If F[] = -1 dv, where the integral is over all space,

(a) Find δExXa/δρ, where ExXa is given by (16.61).
(b) If F[ρ] = ∫ρ-1 Δρ ∙ Δρ dv, where the integral is over all space, and r is a function of x, y, and z that vanishes at infinity, find δF>δρ.