In a wind tunnel experiment the pressure on the upper and lower surfaces of the wings are 0.90$\times {10}^5 \mathrm{Pa} \mathrm{and} 0.91 \times {10}^5 \mathrm{Pa}$ respectively. If the area of the wings is 40${\mathrm{m}}^2 \mathrm{the} \mathrm{net} \mathrm{lifting} \mathrm{force} \mathrm{on} \mathrm{the} \mathrm{wing} \mathrm{is}$

• A

  $2 \times {10}^4 \mathrm{N}$

• B

  $4 \times {10}^4 \mathrm{N}$

• C

  $6 \times {10}^4 \mathrm{N}$

• D

  $8 \times {10}^4 \mathrm{N}$