The number of stereoisomers possible for [Co(ox)₂(Br)(NH₃)]^2$$-$$ is ___________. [ox = oxalate]

A ball weighing 10 g is moving with a velocity of 90 ms^$$-$$1. If the uncertainty in its velocity is 5%, then the uncertainty in its position is ___________ $$\times$$ 10^$$-$$33 m. (Rounded off to the nearest integer)

[Given : h = 6.63 $$\times$$ 10^$$-$$34 Js]

The NaNO₃ weighed out to make 50 mL of an aqueous solution containing 70.0 mg Na⁺ per mL is _________ g. (Rounded off to the nearest integer)

[Given : Atomic weight in g mol^$$-$$1 - Na : 23; N : 14; O : 16]

Let f(x) be a differentiable function at x = a with f'(a) = 2 and f(a) = 4.

Then $$\mathop {\lim }\limits_{x \to a} {{xf(a) - af(x)} \over {x - a}}$$ equals :