arrange the unstable isotopes in decreasing order based on the length of their half-life.
carbon-14 (5.73 x 10^3 years)
argon-39 (2.69 x 10^2 years)
hafnium-182 (9 x 10^6 years)
krypton-81 (2.29 x 10^5 years)
calcium-41 (1.03 x 10^5 years)
iron-60 (1.5 x 10^6 years)
please help lol
