Youre Doing Great (YDG) has four different types of expenses. The total cost for each of the expenses at different volume levels is provided below. Which expense(s) is a variable cost?

	Total Cost at 1,000 units	Total costs at 2,000 units	Total costs at 3,000 units
Expense 1	$5,000	$10,000	$15,000
Expense 2	$6,000	$7,000	$8,000
Expense 3	$3,000	$6,000	$9,000
Expense 4	$12,000	$12,000	$12,000

A) Expense 2 and 4

B) Expense 1 and 3

C) Expense 4

D) Expense 1, 2, and 3

E) Expense 1