user: Question: What is the Tier when the runner-up is Chanda Rubin Caroline Vis?
Columns: ['Week of', 'Tier', 'Winner', 'Runner-up', 'Semi finalists']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['2 October', 'Tier IV', 'Shi-Ting Wang 6–1, 6–1', 'Jing-Qian Yi', 'Tina Križan Annabel Ellwood']
SQL:

assistant: SELECT "Tier" FROM "Table" WHERE "Runner-up" = 'Chanda Rubin Caroline Vis';