Final answer:
Chaucer's tone towards the Merchant is biting, highlighting the irony of the Merchant's public image versus his actual financial situation.
Step-by-step explanation:
The tone Chaucer is taking towards the Merchant in the quote "This estimable Merchant so had set / His wits to work, none knew he was in debt" is biting. The selection from 'The Canterbury Tales' reveals an ironic and slightly sarcastic view of the Merchant's situation. Chaucer is highlighting the Merchant's cunning and deceit in managing his public image, despite his financial difficulties.