By writing up the definition of \( \Delta H \) and \( \Delta L \), and putting all assumed known terms \( H^n \) and \( L^n \) on the right-hand side, we have $$ H^{n+1} = H^n + a\Delta t H^n - b\Delta t H^n L^n $$ $$ L^{n+1} = L^n + d\Delta t H^nL^n - c\Delta t L^n $$

Note:

• These equations are ready to be implemented!
• But to start, we need \( H^0 \) and \( L^0 \)
  (which we can get from the data)
• We also need values for \( a \), \( b \), \( d \), \( c \)