Step 1 — Relevant industry

Bouygues is a diversified industrial group with construction, telecom, media, and energy/services exposure. It does not fit cleanly into the provided regulated utilities, E&P, unregulated power/gas, or transportation infrastructure methodologies as a whole. Therefore, I apply the general corporate baseline formulas.

Step 2 — Estimate Adjusted EBITDA

Reported/reconstructed EBITDA can be approximated from operating profit plus depreciation/amortization and impairment/provision expense.

Given:
- Profit from operating activities = €1,872m
- Depreciation and amortisation expense = €2,228m
- Depreciation of right-of-use assets = €446m
- Impairment/provision expense = €172m
- Nonrecurring operating income = €93m
- Nonrecurring operating expense = €183m

A practical EBITDA reconstruction:
- EBITDA before nonrecurring normalization = 1,872 + 2,228 + 446 + 172 = €4,718m

Normalize nonrecurring items:
- Add back nonrecurring losses: +€183m
- Remove nonrecurring gains: -€93m

Adjusted EBITDA:
- 4,718 + 183 - 93 = €4,808m

Step 3 — Estimate FFO

Baseline:
FFO = Adjusted EBITDA - cash interest - cash taxes

Given:
- Interest paid = €260m
- Income taxes paid = €518m

FFO:
- 4,808 - 260 - 518 = €4,030m

This is close to the company’s cash-flow-before-working-capital style figure:
- Cash flow after cost of net debt, lease interest and income taxes paid = €3,324m
- Add back cost of net debt and lease interest = €260m
- This gives €3,584m before interest/tax financing effect, but includes various company-specific adjustments and excludes/handles some noncash items differently. For S&P-style FFO using EBITDA less cash interest and cash taxes, €4,030m is a reasonable estimate.

Step 4 — Estimate Adjusted Debt

Baseline:
Adjusted Debt = reported debt + leases + other debt-like items - eligible cash

Use balance sheet borrowings and lease liabilities:
- Long-term borrowings = €11,586m
- Current borrowings/current portion = €1,361m
- Current overdrafts and short-term bank borrowings = €418m
- Noncurrent lease liabilities = €2,107m
- Current lease liabilities = €498m

Gross debt including leases:
- 11,586 + 1,361 + 418 + 2,107 + 498 = €15,970m

Eligible cash:
- Cash and cash equivalents = €5,736m

Adjusted Debt:
- 15,970 - 5,736 = €10,234m

Step 5 — FFO / Adjusted Debt

FFO / Adjusted Debt:
- 4,030 / 10,234 = 0.3937854211

Rounded to four decimals:

<answer>0.3938</answer>