= = 10. Letting R = xi + yj + zk, and R |R|, write the vector field F R/R³ in terms of R and e,. (a) Show that div F is identically zero throughout the domain of definition of F. (b) Show that the surface integral of the normal component of F over the surface of the unit sphere r = 1 is 4. (c) Explain why parts (a) and (b) do not contradict the divergence theorem. (d) What is the surface integral of the normal component of F over the surface of a unit sphere with center 4 units away from the origin?