The equivalent conductance of NaCl at concentration C and at infinite dilution are $${\lambda _C}$$ and $${\lambda _\infty }$$, respectively. The correct relationship between $${\lambda _C}$$ and $${\lambda _\infty }$$ is given as: (where the constant B is positive)

The correct set of four quantum numbers for the valence elections of rubidium atom (Z= 37) is:

The variance of first 50 even natural numbers is

$$\mathop {\lim }\limits_{x \to 0} {{\sin \left( {\pi {{\cos }^2}x} \right)} \over {{x^2}}}$$ is equal to :