D shaped groups

Hello Sir,

Could you please tell me how do we decide what is the date of acquisition in D shaped groups?

e.g. question 37 (BPP practice and revision KIT)

1.
B acquired 60% of the share capital of J on 01.01.2002 and 10% of G on 01.01.2003.
J acquired 70% of the share capital of G on 01.01.2003.

In my opinion,
01.01.2002 is date of acquisition between B and J.
01.01.2003 is date of acquisition between B and G.
Since acquisition of 10% of G by B occurred on the same date as acquisition of 70% of G by B, we should consider acquisition of 10% of G as control interest increase which does not influence W2 goodwill calculation.

2.
B acquired 60% and 10% of the share capital of J and G on 01.01.2003 respectively.
J acquired 70% of the share capital of G on 01.01.2002.

Date of acquisition is 01.01.2003 because that is the date when J and G become Subsidiary.

Could you please advise if my understanding is correct?

Thank you in advance.