user: ### NOW ANSWER:
Question: what is the [a] (mol/l) where [hpo 4 2− ]/[a] (%) is 0.612?
Columns: ['[A] (mol/L)', 'pH', '[H 3 PO 4 ]/[A] (%)', '[H 2 PO 4 − ]/[A] (%)', '[HPO 4 2− ]/[A] (%)', '[PO 4 3− ]/[A] (%)']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1', '1.08', '91.7', '8.29', '6.20×10 −6', '1.60×10 −17']
SQL:

assistant: SELECT COUNT("[A] (mol/L)") FROM "Table" WHERE "[HPO 4 2− ]/[A] (%)" = '0.612';