the variable j column number is set to any value of 1 to n in the step s 419 in the step s 420 the defect points of all rows i 1 to m 1 of the jth column are read the m 1th row means a row of u201c total defect points for each educational material unit u201d in the table 35 in the step s 421 it is judged whether the total defect points d m 1 j for each educational material unit is at least the threshold value or not as the threshold value 70 points is set for example if it is lower than the threshold value the process returns from the step s 424 to s 420 and proceeds to processing the next column in the educational material unit defect point table 35 if it is the threshold value or more the process proceeds to the step s 422 in the step s 422 the variable k is incremented by 1 in the step s 423 the value of the variable j is put in the element wd k of the defective educational material unit number table 36 0109 fig1 shows a content of the defective educational material unit number table 36 in the table 36 the number j of educational material unit 37 in the illustrated example whose total defect point is the.