The Crystal Field Stabilisation Energies $(CFSE)$ of high spin and low spin $d^6$ metal complexes in terms of $\Delta_o$,respectively are

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $[CoCl(NH_3)_5]^{2+}$ absorbs at a lower wavelength of light with respect to $[Co(NH_3)_5(H_2O)]^{3+}$.
Reason $R$: It is because the wavelength of the light absorbed depends on the oxidation state of the metal ion.
In the light of the above statements,choose the correct answer from the options given below:

What is the spectrochemical series? Explain the difference between a weak field ligand and a strong field ligand.

Which ligand among the following has the highest splitting power of $d$-orbitals of the central metal ion?

The crystal field stabilization energy of $[Co(NH_3)_6]Cl_3$ is $......... \Delta_0$

Which sets of the $d$-orbitals are directly oriented towards the ligands in octahedral coordination compounds?