A man lent Rs. 25000 for one year under compound interest, to five persons. He lent Rs.5500 at 5% p.a. to the first person, Rs 4000 at 13/2 % p.a. to the second person, Rs.3500 at 11/2% p.a to the third person and Rs.7000 at 17/2% p.a. to the fourth person. At what rate of interest should he lend the remaining amount so that he gets an interest at 8% p.a. on the entire amount?