rectifiaction in 3b

if tax is 100 rs n ITC taken wrongly 200 rs instead of 50 rs then n then eligible rev ITC wud be 150 but on what amount interest will hv to paid. 200 or 150 ?Acc. to rule on 200 but genuinely party take benifie of 150 only so he sud pay int on 150. Plz guide .