If you ask me to give you a rough estimate for the cost of the project, ___________ I would say thirty lakhs.

The blank needs an idiom meaning to give an immediate, spontaneous response without preparation.

Option 1 -> off-the-mike -> means away from the microphone; not relevant to giving estimates.

Option 2 -> off-the-mark -> means inaccurate or wrong; doesn't fit the context of giving estimates.

Option 3 -> off-the-cuff -> means spontaneous or improvised without preparation; perfect for giving rough estimates.

Option 4 -> off-the-grid -> means disconnected from utilities or systems; irrelevant to estimates.

When someone asks you for a quick estimate and you don't have time to calculate precisely, you give an off-the-cuff response. It's like rolling up your shirt sleeves and giving your best guess on the spot, without formal preparation or detailed analysis.