For an impairment in the goodwill of a subsidiary, Steve Scott will give you the necessary information. It’s not likely that you will need to calculate the fall in value of an investment in an associate at this level. That treat lies in store for you at P2.
Impairment of goodwill is no longer an automatic affair ( it used to be eg goodwill is written off over 10 years ) but that has changed. Goodwill is now subject to an annual impairment review and adjusted accordingly. Some years the directors may decide that goodwill is not impaired and other years they may decide that it is impaired.