The relation between active risk, information ratio, and active risk aversion is as follow:

$$\lambda a = \frac{\text{IR}}{(2 * \psi p)} \\ \lambda a = \frac{0.5}{(2 * 0.05)} = 5$$

It is important to bear in mind that in the risk aversion equation above, the desired level of active risk is measured in percentage points rather than in decimal form. Remember that active risk is just another name for tracking error.