Financial gearing

Ques.179 – p.69 (BPP Revision Kit)
The following is an extract of ELW’s statement of financial position:

$1 ordinary share capital 100
Retained earnings 400
Total equity 500

Loan notes 500

The ordinary shares are currently quoted at $5.50, and loan notes are trading at $125 per
$100 nominal.
What is ELW’s financial gearing ratio (debt/debt + equity) using market values (to the
nearest %)?

The correct answer is 15% = 625/(550+625)
However, I wonder why retained earnings is not included in the above calculation, isn’t it part of equity?

Looking forward to your response,
Iniss.