Helium burning occurs via the "triple alpha" reaction: 34he12c which occurs at the rate r3a where na denotes the number fraction 4he. once there is any 12c present then we can also get the reaction: 1ad: soma 12c(a,)160 which occurs at the rate r12a n12na012a 1o once some 10o has been produced where n12 is the number fraction of 12c. furthermore then we additionally get 160(a,)20ne occurring at the rate r16a n16na016a where n16 is the number abundance of 16o. similarly, let n20 be the number fraction of 20ne. question 2 write down the differential equations for na, n12, n16 and n20 as a function of time in terms of the r defined above