A company's current assets of MXN 45,000,000 include unrestricted cash of MXN 8,000,000, cash restricted in escrow for debt service for more than 12 months of MXN 4,000,000, accounts receivable of MXN 16,000,000, inventories of MXN 14,000,000 and prepaid expenses of MXN 3,000,000. Current liabilities are MXN 20,000,000. What is the acid-test ratio (prueba del ácido)?