A green plant contains radioactive C  14 and C  12 isotope. If in a sample of dead old wood of this plant 2.5×10-6 mol14C and 7.5×10-6 mol14 N are present then calculate value of Z. Assuming all ‘N’ is obtained due to disintegration of  14C.Where Z=Age of woodtHalf life of 14C isotopet1/2