where  𝑗 is the degree of extent for the j-th reaction, dnpj is the change in the amount of substance for Rp by the j-th reaction, and pj is the stoichiometric coefficient for Rp in the j-th reaction (pj is defined as negative for reactants and positive for products, and npj /pj is independent of p). According to this definition, -d𝐶 1 d𝑡 ⁄ in equation ( ) is expressed as  𝑉 ⁄ . The quantity Aj in equation (3b) is the affinity of the j-th reaction, given as 𝐴 𝑗 = -∑  𝑝𝑗 𝜇 𝑝 𝑝 . 11 Thus,  𝑗 refers to the rate of the j-th reaction, as previously mentioned, and Aj /T is the thermodynamic force. The rate  𝑗 can be expressed using Aj as