What is IUPAC name of $\left(\mathrm{CH}_3\right)_4 \mathrm{C}$ ?

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