Assume that a company provided the following excerpts of information from its flexible budget performance report:

Actual Results Flexible Budget Planning Budget

Flights $($q$)52?$question mark $?$question mark

Expenses:

Wages and salaries $($$$4,000+$ $$88\mathrm{.}00$q$)$ $ $8,510?$question mark $ $8,400$

What is the activity variance for wages and salaries expense?