{ diff(x1, t) = (1*k90*k4*(k1/(1 + k74/k72) + k65)*(k67 - x1*k90 - x2*k90)/(k5 + k67 - x1*k90 - x2*k90)/k90 + (-1)*k90*(k51 + k6*x11*k90)*x1*k90/(k7 + x1*k90)/k90)/k90,
  diff(x2, t) = (1*k90*(k8 + k12*x10*k90)*(k67 - x1*k90 - x2*k90)/(k9 + k67 - x1*k90 - x2*k90)*k10/(k10 + (x4*k90 + x5*k90)/(1 + k76/k73))/k90 + (-1)*k90*k11*x2*k90/(k13 + x2*k90)/k90)/k90,
  diff(x3, t) = (1*k90*(k14 + k15*x6*k90/(k16 + x6*k90))/k90 + (-1)*k90*k17*x3*k90/k90)/k90,
  diff(x4, t) = (1*k90*k18*x3*k90/(k19 + x3*k90)/k90 + (-1)*k90*k25*x4*k90/k90 + (-1)*k90*(k20*x1*k90 + k21*x9*k90/(1 + k75/k60))*x4*k90/(k22 + x4*k90)/k90 + 1*k90*(k23 + k59*x11*k90)*x5*k90/(k24 + x5*k90)/k90)/k90,
  diff(x5, t) = (1*k90*(k20*x1*k90 + k21*x9*k90/(1 + k75/k60))*x4*k90/(k22 + x4*k90)/k90 + (-1)*k90*(k23 + k59*x11*k90)*x5*k90/(k24 + x5*k90)/k90)/k90,
  diff(x6, t) = (1*k90*k26*x5*k90/(1 + k76/k73)*(k68 - x6*k90 - x13*k90)/(k27 + k68 - x6*k90 - x13*k90)/k90 + (-1)*k90*(k52 + k28*x11*k90)*x6*k90/(k29 + x6*k90)/k90)/k90,
  diff(x7, t) = (1*k90*(k30 + k31*x6*k90/(k32 + x6*k90))/k90 + (-1)*k90*k33*x7*k90/k90)/k90,
  diff(x8, t) = (1*k90*k34*x7*k90/(k35 + x7*k90)/k90 + (-1)*k90*(k40 + k41*x10*k90)*x8*k90/(k42 + x8*k90)/k90 + (-1)*k90*(k36*k2 + k66)*x8*k90/(k37 + x8*k90)/k90 + 1*k90*k38*x9*k90/(k39 + x9*k90)/k90)/k90,
  diff(x9, t) = (1*k90*(k36*k2 + k66)*x8*k90/(k37 + x8*k90)/k90 + (-1)*k90*k38*x9*k90/(k39 + x9*k90)/k90)/k90,
  diff(x10, t) = (1*k90*k43*x1*k90*(k69 - x10*k90)/(k44 + k69 - x10*k90)/k90 + (-1)*k90*(k53 + k45*x11*k90)*x10*k90/(k46 + x10*k90)/k90)/k90,
  diff(x11, t) = (1*k90*k47*x1*k90*(k70 - x11*k90)/(k48 + k70 - x11*k90)/k90 + (-1)*k90*k49*x11*k90/(k50 + x11*k90)/k90)/k90,
  diff(x12, t) = (1*k90*(k54*x9*k90/(1 + k75/k61) + k55*x1*k90)*(k71 - x12*k90)/(k56 + k71 - x12*k90)/k90 + (-1)*k90*k57*x12*k90/(k58 + x12*k90)/k90)/k90,
  diff(x13, t) = 1*k90*(k62*(k68 - x6*k90 - x13*k90)*(k77 - x13*k90) - k63*x13*k90)/k90/k90 }