Mumbai: The Indian Rupee on Monday plunged by 28 paisa to hit its weakest level in eight weeks at 75.40 against the US dollar in line with massive erosion in domestic stocks amid concerns over the new Omicron variant.At the interbank foreign exchange market, the local currency opened weak at 75.22 and witnessed an intra-day high of 75.19 and a low of 75.45 against the US dollar in the day trade.