$k_{m}=$ transcription rate of mRNA

$\delta([mRNA],[siRNA])=$ rate of mRNA degraded by siRNA

$\frac{d[mRNA]}{dt}=k_{m}-\delta([mRNA],[siRNA])$

$k_{T}=$ rate of protein translation

$d_{p}=$ decay rate of protein

$\frac{d[protein]}{dt}=k_{T}[mRNA]-d_{p}[protein]$

Finding $\delta([mRNA],[siRNA])$

$\lambda=$ affinity of siRNA target site for siRNA guided RISC complex

$\kappa=$ mRNA cleave + dissociation rate of bound siRNA RISC

$siRNA^{*}=$ siRNA loaded (active) RISC complex

$siRNA^{*}_{bound}=$ mRNA bound siRNA^{*} complex

Rate of mRNA degradation/decay

$mRNA\xrightarrow[\text{deg_{nonspec}}]{\text{}}degmRNA$