**Reasoning**

1. **Determine total adjusted capital (debt + equity).**  
   - Equity (total) = €2,755,243 k.  
   - Financial debt = “Other Non‑current Financial Liabilities” (€4,722,263 k) + “Other Current Financial Liabilities” (€619,418 k) = €5,341,681 k.  
   - **Total adjusted capital** = €2,755,243 k + €5,341,681 k ≈ €8,096,924 k.

2. **Compute the S&P‑allowed equity‑credit ceiling for hybrids.**  
   - 15 % of total adjusted capital = 0.15 × €8,096,924 k ≈ €1,214,539 k.  
   - This is the maximum amount of hybrid bonds that can receive equity credit.

3. **Assess the company’s current capital structure and financing needs.**  
   - Debt‑to‑equity ratio ≈ 1.94, indicating a highly leveraged balance sheet.  
   - Free cash flow after capex is negative (‑€323 M), and the current ratio is below 1 (0.88), showing liquidity pressure.  
   - Interest coverage is moderate (≈ 5×), but the firm still needs external financing to fund its large investment programme and dividend payments.

4. **Consider the cost and rating impact of hybrid issuance.**  
   - Market data (2022 swap curves and iShares corporate‑bond yields) suggest hybrid financing can be obtained at a relatively low coupon (≈ 2–3 %).  
   - Because hybrids receive equity credit, issuing up to the 15 % ceiling would improve the reported leverage ratio (debt/equity would fall from ~1.94 to ~1.35) and could support the current investment‑grade rating.  
   - Staying within the cap avoids the penalty that S&P applies when equity credit exceeds the limit.

5. **Determine the appropriate usage level.**  
   - Given the firm’s high leverage, negative free cash flow, and the benefit of equity‑credit hybrids, the most advantageous strategy is to utilize the full allowed capacity.  
   - Using the maximum permissible amount (≈ €1.2 bn) provides the greatest balance‑sheet improvement without breaching S&P’s guideline.

**Conclusion:** The company should issue hybrid bonds up to the S&P cap—i.e., 100 % of the allowable equity‑credit limit.

<answer>100%</answer>