A boy has a mass of 20 kg and the area of the sole of one of his feet is 0.01 m². Given the following additional conditions:

1. The boy is carrying a backpack that has a mass equal to 10% of his mass.
2. The boy is standing on a floor that exerts an additional upward force equal to 5% of the total weight of the boy and the backpack due to the elasticity of the floor.
3. The acceleration due to gravity is g = 10 m/s².

Calculate the pressure exerted on the floor when the boy is standing on one foot, considering all the above conditions. Provide the final pressure in N/m², rounded to the nearest integer.

1. Calculate the mass of the backpack:
  - Mass of the backpack = 10% of the boy's mass = $0.1\times 20 \text{kg}=2 \text{kg}$

2. Calculate the total weight (force due to gravity):
  - Total weight = Total mass $\times g=22 \text{kg}\times 10 {\text{m/s}}^2=220 \text{N}$

3. Calculate the additional upward force due to the floor's elasticity:
  - Additional upward force = 5% of the total weight = $0.05\times 220 \text{N}=11 \text{N}$

4. Determine the effective downward force:
  - Effective downward force = Total weight - Additional upward force = $220 \text{N}-11 \text{N}=209 \text{N}$

5. Calculate the pressure exerted on the floor:
  - Pressure = Effective downward force / Area of one foot = $209 \text{N}/0.01 {\text{m}}^2=20900 {\text{N/m}}^2$

Therefore, the final pressure exerted on the floor when the boy is standing on one foot is 20900 N/m².