A typical fixed cost is the purchase of the mining rigs and setup of the operation facility. Let I be the fixed cost per 1.0 energy power. Although I is usually described in fiat term, it can be converted to the equivalent energy amount by the introduction of electricity fee rate (the U as mentioned here). Therefore the equation:

$0=K I + \sum_{t_0 \le \frac{t}{210000} <t_1} {K T-\left(C+F \right)P}$

Simplify then:

$P=\frac{K \left(T+\frac{I}{210000 \left(t_1-t_0 \right)} \right)}{F+C}$

As usual, initial fixed cost tends to be averaged out as longer as the business running.