Find the total number of moles of donor atoms present in one mole trioxalatocobaltate(III) ion.

Calculate the molar mass of non volatile solute when 5 g of it is dissolved in 50 g solvent, boils at $119.6^{\circ} \mathrm{C}$. $\left[\mathrm{K}_{\mathrm{b}}=3.2 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right.$, boiling point of pure solvent $=118^{\circ} \mathrm{C}$ ].

Two tangents drawn from $\mathrm{P}(1,7)$ to the circle $x^2+y^2=25$, touch the circle at Q and R respectively. The area of the quadrilateral PQOR is

Let $X=\left[\begin{array}{l}\mathrm{a} \\ \mathrm{b} \\ \mathrm{c}\end{array}\right], \mathrm{A}=\left[\begin{array}{ccc}1 & -1 & 2 \\ 2 & 0 & 1 \\ 3 & 2 & 1\end{array}\right]$ and $\mathrm{B}=\left[\begin{array}{l}3 \\ 1 \\ 4\end{array}\right]$. If $A X=B$, then the value of $2 a-3 b+4 c$ will be