How do I fix this problem for my query

Query Tools Access External Data Database Tools Design Tell me what you want to do -Property Sheet Table Names Union (Insert Rows X Delete Rows ABuk Insert Columns Pass-Through Data Definition Delete Columns end Update Crosstab Delete Show Table Totals Parameters Return: Query Type Query Setup Show/Hide Query SELECT Room,count (Student Numben) as TotaiStudents from Class INNER JOIN Enrollment on Class.Name-Enrollment Class, Name Microsoft Access Your query does not indude the specified expression 'Roon' as part can aggregatenction. rch