A) Outline 4 characteristics of the Normal distribution and b) Calculate the number of recruits with an IQ between 100 and 115.

Total number of recruits ($N$) = 20,000
Mean ($\mu$) = 108
Variance ($\sigma^2$) = 49
Standard deviation ($\sigma$) = $\sqrt{49} = 7$

The z-score formula is $Z = \frac{X - \mu}{\sigma}$.

For $X_1 = 100$:

For $X_2 = 115$:

This is equivalent to finding $P(-1.14 < Z < 1.00)$.
Using a standard normal distribution (Z-table):
$P(Z < 1.00) = 0.8413$
$P(Z < -1.14) = 0.1271$

The probability is:

Number of recruits = Total recruits $\times$ Probability

The number of recruits with an IQ between 100 and 115 is $\boxed{14284}$.