Six files in a directory are labelled $P,Q,R,S,T,$ and $U$. You are tasked with identifying specific files based on their system attributes:

(i) Files $P,Q,$ and $R$ are Word Documents $($docx$)$, while $S,T,$ and $U$ are Excel Spreadsheets $($xlsx$)$
(ii) Files $Q,R,T,$ and $U$ are marked as Read-only, while the others are Editable
(iii) Files $P,Q,$ and $S$ are backed up to the Cloud, while the others are stored only on the Local Disk

Which two files are Read-only, Excel Spreadsheets stored only on the Local Disk?