Thanks for the query.

The answer should be 60 is the answer because first two times it is being added to 4. 4+4 = 8 and 8+4 = 12.

Then 12+8 = 20 and 20+8 = 28, 8 is being added two times, both to 12 and to 20.

Then 28+16 = 44, now 16 is being added.Since 4 and 8 had been added two times,16 should also be added two times.

So, 44+16 = 60(Ans)