In the above network, current flows from $\mathrm{N}$ to $\mathrm{T}$ when
(1) p closed, q closed, ropened and s opened.
(2) p closed, q opened, s closed and r opened.
(3) q closed, p opened, $\mathrm{r}$ opened and s closed.
(4) p opened, q opened, $\mathrm{r}$ closed and s closed.