In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{520}\,\,\,\text{:}\,\,\,\,\text{420}\] \[\text{760}\,\,\,\text{:}\,\,\,\,\text{660}\] \[\text{110}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  70                         
• B.         210       
• C.  60                         
• D.         10