What is the max unit price of rock tracks?
select max(t2.unitprice) from genre as t1 join track as t2 on t1.genreid = t2.genreid where t1.name = "Rock"
What is the average?
select avg(t2.unitprice) from genre as t1 join track as t2 on t1.genreid = t2.genreid where t1.name = "Rock"