NEW DELHI: Six of the 10 most valued Indian firms suffered a combined erosion of Rs 42,827.39 crore in market valuation last week, with IT major TCS taking the biggest hit.Among the top 10 firms, ITC, HUL, Kotak Mahindra Bank and ICICI Bank made gains in their market capitalisation (m-cap) for the week ended Friday, while Reliance Industries Ltd (RIL), TCS, HDFC Bank, HDFC, Infosys and SBI finished with losses.The m-cap of Tata Consultancy Services (TCS) slumped Rs 14,146.5 crore to Rs 7,55,636.47 crore.HDFC Bank's valuation plunged Rs 9,967.3 crore to Rs 6,16,869.80 crore and that of RIL dropped Rs 8,327.77 crore to reach Rs 8,50,628.63 crore.The m-cap of HDFC declined Rs 5,198.74 crore to Rs 3,48,806.25 crore and that of Infosys tumbled Rs 3,669.9 crore to Rs 3,26,730.54 crore.SBI's valuation also fell by Rs 1,517.19 crore to Rs 2,81,393 crore.On the other hand, the m-cap of ITC zoomed Rs 13,423.2 crore to Rs 3,74,623.78 crore.HUL's valuation jumped Rs 13,237.17 crore to Rs 3,72,513.16 crore and ICICI Bank gained Rs 2,549.65 crore to stand at Rs 2,54,278.86 crore.Also, Kotak Mahindra Bank added Rs 2,039.41 crore to its m-cap to reach Rs 2,56,822.96 crore.In the ranking of top 10 firms, RIL remained at the number one place, followed by TCS, HDFC Bank, ITC, Hindustan Unilever Ltd (HUL), HDFC, Infosys, SBI, Kotak Mahindra Bank and ICICI Bank.During the last week, the BSE benchmark Sensex fell 95.12 points or 0.24 per cent to close at 38,767.11 on Friday.