Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:

Convert text to sql: What is the age of the friend of Zach with longest year relationship? | person : name , age , city , gender , job | personfriend : name , friend , year | personfriend.friend = person.name | personfriend.name = person.name | 

### Response:

select _ from _ where _ = ( select max ( _ ) from _ where _ ) | select person.age from person join personfriend on person.name = personfriend.friend where personfriend.name = 'Zach' and personfriend.year = ( select max ( year ) from personfriend where name = 'Zach' )