The two tanks A and $B$ shown below are connected using a manometer. Oil is poured into tank $A$ to a depth of $h=1\mathrm{.}25m.$ Air is also trapped in line $CD$ as shown. Assume ${}_{\text{o}\text{l}\text{l}}=800k\frac{g}{m^3}$ and ${}_{\text{w}\text{a}\text{t}\text{e}\text{r}}=1000k\frac{g}{m^3}.$

a$.$ Determine the pressure of the trapped air in $tankB,$ in kPa $.[15$ points$]$

b$.$ The lid of tank $B$ is suddenly removed and the tank is now open to the atmosphere. A worker replaces line CD$,$ which now contains mercury. All other fluids and their respective heights remain the same. Calculate the difference in elevation between points $C$ and $D(h_{CD}),$ in m $.[15$ points$]$