Suppose J$($r$)$J$($r$)$ is constant in time, so $($Problem $7\mathrm{.}60)$ $($r$,$t$)=$$($r$,0)+$$($r$,0)$t$($r$,$t$)=$$($r$,0)+$$($r$,0)$t$.$ Show that

E$($r$,$t$)=14$$$d$$$($r$,$t$)$R$^$R$2$E$($r$,$t$)=14$$$d$$$($r$,$t$)$R$^$R$2$

that is$,$ Coulomb's law holds with the charge density evaluated at the non$-$retarded time.