The quarterly operating statement for a firm gives the following information: Number of pieces manufactured: 100 Number of pieces sold: 100 Total cost of goods sold: $800 Average cost of single piece: $5 Net sales: $1,000 It can be inferred that the firm's gross margin is _____. Group of answer choices

A. $92
B. $2
C. $1800
D. $200
E. $1818