Consolidation with minority interest

Struggling with this kind of problems. If you know the logic behind pls help!
P.Co. and S.Co. each make up their account on 31st of December. P. Co. buys 80% of
the 100.000 ordinary shares of S.Co. for 175.000 on the 1st of January. S.Co’s retained
earnings stood at 60.000 on the 31st of December. S.Co’s profit after tax for the year 31st
of December 20X7 were 20.000. In January 20X8 S.Co declared a first and final dividend
for 20X7 of 10.000.
At the 31st of December 20X7 P. Co’s retained earnings stood at 110.000. This does not
include adjustments for dividends receivable from S.Co.
Prepare the consolidation of P. Group as of the 31st of December 20X7.
a) retained earnings?
b) non controlling interest?
c) goodwill