# Carrier frequency of chirp signal

I am computing the link budget for a communication-radar (CoRadar) system. The formula for maximum distance, in communication, is:

$$d_{max} = \sqrt{\frac{P_t}{\tau}\frac{G_t G_{r, comm} \lambda^2}{(4\pi^2)FkT_0 B_w SNR_{comm}}}$$

where,

$$P_t$$ is the transmitted power

$$\tau$$ is the duty cycle

$$G_t$$ is the transmission antenna gain

$$G_{r, comm}$$ is the communication receiver antenna gain

$$\lambda$$ is the wavelength

$$F$$ is the noise factor

$$k$$ is the Boltzmann's constant

$$T_0$$ is the noise reference temperature

$$B_w$$ is the bandwidth

$$SNR_{comm}$$ is the $$SNR$$ of the communication system

I am using a LFM chirp signal that sweeps from $$3.5\times10^6$$ to $$8.5\times10^6$$. Which would be the frequency, which would be associated to a wavalength $$\lambda$$, that should I use for the formula? $$8.5\times10^6$$? Or, $$\frac{8.5\times10^6 + 3.5\times10^6}{2} = 6\times10^6$$ (i.e. a middle point)?

And which would be the bandwidth? $$8.5\times10^6 - 3.5\times10^6 = 5\times10^6$$?

Many thanks.