In a certain code language,
'K + L' means 'K is the mother of L',
'K - L' means 'K is the sister of L',
'K × L' means 'K is the husband of L',
'K ÷ L' means 'K is the father of L'.
How is R related to U if 'P × Q - R ÷ S + T - U'?
1
father
2
Mother's father
3
son
4
Father's father