Write the formula of the following compounds according to the `IUPA` rule
(a) Potassium tetraxoferrate (VI)
(b) Potassium tetrazidocobalt(II)

Explanation

To write the formulas of the given compounds according to the IUPAC rules, we will follow these steps for each compound.

### (a) Potassium tetraoxoferrate (VI)

1. **Identify the central metal and its oxidation state**:
- The central metal is iron (Fe), and it is in the +6 oxidation state (VI).

2. **Identify the ligands and their charges**:
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