Corrections and Score 1987 AP Exam

I corrected my test and got -18/47 = 38%
Corrections:     % of students that got the question wrong:
 1. c                     39%
 2. a                     49%
 6. d                     27%
 7. e                     48%
15. a                     56%
19. a                     58%
21. e                     31%
22. e                     43%
25. c                     77%
28. c                     28%
48. a                     41%
49. c                     52%
51. c                     68%
54. b                     42%
55. a                     76%
56. b                     43%
59. e                     79%
60. b                     55%

To calculate my score I assumed I'd miss 38% of the questions we skipped (-5) and I used scores I usually got on other AP practice essays in previous years (3, 5, 4). Using the guide at the end of the test I calculated that I would have received a 3 on the exam with a composite score of 71.484.