M, N, O, P, Q, R, and S live on seven different floors of a building numbered from 1 (lowest) to 7 (highest). Each person has a unique income from the...

M, N, O, P, Q, R, and S live on seven different floors of a building numbered from 1 (lowest) to 7 (highest). Each person has a unique income from the set {3500, 15000, 7500, 9000, 11000, 13500, 5000}. The following conditions apply:

• M lives on an odd-numbered floor but not on floor 3.
• The person earning 11000 lives immediately above M.
• Exactly two people live between M and the person earning 7500.
• The person earning 15000 lives on an odd-numbered floor above P.
• Exactly three people live between O and the person earning 15000.
• The person earning 7500 lives immediately above O.
• R earns 4000 more than Q.
• The person earning 3500 lives immediately above the person earning 5000.
• Exactly one person lives between N and Q, with N living above Q.
• Neither O nor M earns 9000.
• Q does not earn 7500.

Question: If all the people are arranged in alphabetical order from top (floor 7) to bottom (floor 1), how many people will remain in their original floor positions?