Significant portions of their assets have frequently been financed by large dealer banks through short-term (overnight) repurchase agreements, where creditors possess bank securities as a safeguard against default losses. Below is a table showing the quarter-end financing distribution for four A-rated broker-dealer banks, with all figures expressed in USD billion.

Financial instruments	Bank P	Bank Q	Bank R	Bank S
Owned	656	750	339	835
Pledged as collateral	258	472	139	209
Not pledged	398	278	200	626

Given the scenario where repo creditors become equally concerned about the solvency of each bank, which bank is at the highest risk of encountering a liquidity crisis?