TDS u/s 194C for the FY 2011-12

TDS u/s 194C - Payment to Contractors or Sub-Contractors: (for FY 2011-12) If, a single bill amount for the sub contractor is less than Rs. 20,000 than NO TDS is deducted. But if the another bill received from the same sub-contractor amounting to Rs. 20,000 & next bill amounting to Rs. 40,000 than on which amount the TDS will be deducted ? It will be on aggregate 80,000 or only 5,000 (80,000-75,000)

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