The following table gives the distribution of the lifetime of neon lamps. Lifetime(in hours) More than or equal to 1500 More than or equal to 2000 More than or equal to 2500 More than or equal to 3000 More than or equal to 3500 More than or equal to 4000 More than or equal to 4500 More than or equal to 5000 No: of lamps 400 386 330 270 184 110 48 0 Find the median lifetime of a lamp.