If T = 2π√(L/G), make G the subject of the formula. Hence, find the value of G to the nearest whole number when T = 45, L = 8 and π = 3.142.

$$\left(\frac{T}{2\pi}\right)^2 = \frac{L}{G}$$ $$\frac{T^2}{4\pi^2} = \frac{L}{G}$$

$$G = \frac{L}{\frac{T^2}{4\pi^2}}$$ $$G = \frac{4\pi^2 L}{T^2}$$

The formula with $G$ as the subject is $\boxed{G = \frac{4\pi^2 L}{T^2}}$.

$$G = \frac{4 \times (3.142)^2 \times 8}{(45)^2}$$ $$G = \frac{4 \times 9.872164 \times 8}{2025}$$ $$G = \frac{315.909248}{2025}$$ $$G \approx 0.15600456$$

$$G \approx \textbf{0}$$

The value of $G$ to the nearest whole number is $\boxed{0}$.

For 24 persons, the cost is N800.00:

$$800 = k + \frac{m}{24} \quad (1)$$

For 18 persons, the cost is N1200.00:

$$1200 = k + \frac{m}{18} \quad (2)$$

Subtract equation (1) from equation (2):

$$(1200 - 800) = \left(k + \frac{m}{18}\right) - \left(k + \frac{m}{24}\right)$$ $$400 = \frac{m}{18} - \frac{m}{24}$$

Find a common denominator for 18 and 24, which is 72.

$$400 = \frac{4m}{72} - \frac{3m}{72}$$ $$400 = \frac{m}{72}$$ $$m = 400 \times 72$$ $$m = 28800$$

$$800 = k + \frac{28800}{24}$$ $$800 = k + 1200$$ $$k = 800 - 1200$$ $$k = -400$$

So the formula for the cost per person is $C = -400 + \frac{28800}{N}$.

Substitute $N = 42$ into the formula:

$$C = -400 + \frac{28800}{42}$$ $$C = -400 + 685.71428...$$ $$C = 285.71428...$$

$$C \approx \textbf{N286}$$

The cost per person for 42 persons to the nearest naira is $\boxed{\text{N286}}$.