1. Calculate Refractive Index ($\mu$):
$\mu = \frac{c}{v} = \frac{3 \times 10^8}{2 \times 10^8} = 1.5$.

2. Determine Radius of Curvature ($R$):
For a lens with radius of aperture $r = 3 \text{ cm}$ and thickness $t = 0.3 \text{ cm}$, the radius of curvature is given by $R \approx \frac{r^2}{2t}$ (for small thickness).
$R = \frac{3^2}{2 \times 0.3} = \frac{9}{0.6} = 15 \text{ cm}$.

3. Lens Maker's Formula:
$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$. For a plano-convex lens, $R_1 = R$ and $R_2 = \infty$.
$\frac{1}{f} = (1.5 - 1) \left( \frac{1}{15} \right) = 0.5 \times \frac{1}{15} = \frac{1}{30}$.
Thus, $f = 30 \text{ cm}$.

The passage emphasizes that higher productivity no longer ensures wage increases because of other structural factors — exactly what option C states.

Option A is correct.

Share premium is the excess above nominal value when shares are issued. It is recorded in the Share Premium Account, which is a capital reserve — it cannot be distributed as dividends.

This is a $1^\infty$ indeterminate form. Take logarithm:

$\ln p = \lim_{x\to0^+}\dfrac{\ln(1+\tan^2\sqrt{x})}{2x}$

Let $t=\sqrt{x}$, so $x=t^2$, $x\to0^+$ means $t\to0^+$:

$= \lim_{t\to0^+}\dfrac{\ln(1+\tan^2 t)}{2t^2} = \lim_{t\to0^+}\dfrac{\tan^2 t}{2t^2} = \dfrac{1}{2}$

(using $\ln(1+u)\approx u$ for small $u$ and $\lim_{t\to0}\frac{\tan t}{t}=1$)