Let the junction temperature be $T$. In steady state, the heat current through the copper rod equals the sum of currents through brass and steel.

$\frac{K_c A (100 - T)}{L_c} = \frac{K_b A (T - 0)}{L_b} + \frac{K_s A (T - 0)}{L_s}$

$\frac{0.92 \times (100 - T)}{46} = \frac{0.26 \times T}{13} + \frac{0.12 \times T}{12}$

$0.02 (100 - T) = 0.02T + 0.01T \implies 2 - 0.02T = 0.03T \implies 5T = 200 \implies T = 40^\circ\text{C}$.

Rate of heat flow $H = \frac{0.92 \times 4 \times (100 - 40)}{46} = 0.02 \times 4 \times 60 = 4.8 \text{ cal/s}$.

Herd immunity threshold depends on the basic reproduction number (R_0) of the disease:

H = 1 - \\frac{1}{R_0}

For measles, R_0 is 12–18 (highly contagious), making the herd immunity threshold approximately 92–95%. This is why measles can re-emerge even with 90% vaccination coverage. A Head Nurse must understand herd immunity concepts to advocate for achieving high vaccination coverage targets in EPI campaigns.

Using $n_1 u_1 = n_2 u_2$:

$128 \times [\text{kg} \cdot \text{m}^{-3}] = n_2 \times [(50 \text{ g}) \cdot (25 \text{ cm})^{-3}]$

$n_2 = 128 \times \left( \frac{1000 \text{ g}}{50 \text{ g}} \right) \times \left( \frac{25 \text{ cm}}{100 \text{ cm}} \right)^3$

$n_2 = 128 \times 20 \times \left( \frac{1}{4} \right)^3 = \frac{128 \times 20}{64} = 2 \times 20 = 40$.

NACTE — the National Accreditation Council for Teacher Education — is the body in Pakistan responsible for accrediting teacher training programmes and institutions, ensuring they meet national quality standards. It was established to regulate and improve the quality of teacher education across the country.

Correct Answer: C — NACTE.