-Bill's Office Furniture Sells Office Chairs and Desks

-Bill's Office Furniture sells office chairs and desks.Bill's has changed the price per chair by $10 in each of four successive weeks.Figure 5-12 shows the four prices along with the corresponding sales of desks.From this information,it can be seen that

A) office chairs and desks are unrelated goods
B) office chairs and desks are complementary goods
C) office chairs and desks are substitute goods
D) both goods are normal goods
E) both goods obey the law of demand