Dion predicted that he would sell 87 art prints. He actually sold 100 art prints. What are the values of a and b in the table below?
 Percent Error
 Item
 Approximate value
 Exact value
 Error
 Absolute error
 Ratio
 Percent error
 Art prints
 87
 100
 a
 b
 a = negative 13; b = negative 13
 a = negative 13; b = 13
 a = 13; b = negative 13
 a = 13; b = 13