Part $3.$ A differential leveling loop start at a known BM $($Elev $69\mathrm{.}10$ ft $)$ and ends at a known Iron Stake

Elev $=68\mathrm{.}97ft.$ The backsight and foresight distances were kept approximately equal.

Readings $($ in feet$)$ listed in the order taken are:

Setup $1$: BS$)$ to BM$,4\mathrm{.}12($FS$)$ to TP$1$

Setup $2$: $4\mathrm{.}49($BS$)$ to TP$1,2\mathrm{.}80($FS$)$ to Sewer Cover

Setup $3$: $4\mathrm{.}04($BS$)$ to Sewer Cover, $6\mathrm{.}01($FS$)$ to TP$2$

Setup $4$: $5\mathrm{.}26($BS$)$ on TP$2,5\mathrm{.}86($FS$)$ to Iron Stake.

What is the calculated elevation of Sewer Cover? $($Do not adjust in this step$)$

Part $4.$ What is the Error of Closure of the level loop?