STEM tutor is needed to create Olympiad Questions

Our organization conducts Science, Physics and Astronomy Olympiads. We need a specialist who can write 25 challenging, STEM related questions per categories listed below:

Natural Science:
Category 1 - Grade 3 and 4
Category 2 - Grade 5 and 6
Category 3 - Grade 7 and 8
Category 4 - Grade 9 and 10
Category 5 - Grade 11 and 12

Physics and Astronomy:
Category 1 - Grade 7 and 8
Category 1 - Grade 9 and 10
Category 1 - Grade 11 and 12