Q$1.$ For contour mapping, the reduced levels $($RL$)$ of the points were obtained from leveling used by $10m10m$ grid system as follows.

a$.$ Plot the grid with the reduced levels.

b$.$ Determine the area of land limited to the borders of $($location of corners$)$:

B$1-$B$2-$A$2-$A$3-$C$4-$D$3-$C$2-$C$1-$B$1$

c$.$ Find the average slope between points $A2$ and $D3$ in percentage.

$\backslash$table$[[$A$1,50\mathrm{.}20,$A$2,50\mathrm{.}60,$A$3,51\mathrm{.}10,$A$4,51\mathrm{.}50],[$B$1,51\mathrm{.}20,$B$2,51\mathrm{.}60,$B$3,52\mathrm{.}10,$B$4,52\mathrm{.}50],[$C$1,52\mathrm{.}20,$C$2,52\mathrm{.}60,$C$3,53\mathrm{.}10,$C$4,53\mathrm{.}50],[$D$1,53\mathrm{.}20,$D$2,53\mathrm{.}60,$D$3,54\mathrm{.}10,$D$4,54\mathrm{.}50]]$