A weather ballon is partially filled with helium to allow expansion at high altitudes .at stp. that ballon is filled with enough helium to give a volume of 25L. at an altitude of 30km and -35°C. IT HAS EXPANDED TO 2460L. the increase in volume causes the ballon to burst and a small parachutr returns the instruments

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally

4d^55s^1 ( third choice)