D-Group : Date issue

On 1 January 20X3 Murder, a public limited company acquired 60% of Mystery, a public limited company.
On 30 July 20X1 Murder acquired 10% of Suspense, a public limited company, and on the same day Mystery acquired 80% of Suspense.

When i consolidated it , i took net assets @ acquisition figure of Suspense as on 31 July 20X1 (for goodwill calculation) whereas in answer they have taken net assets figure as on 1 January 20X3.So how is that ???? Goodwill is calculated on acquisition right so murder acquired control on suspense on 30 July 20X1 , so goodwill shouldn’t be calculated on that date???????