Pcab = 0.78 atm = 79,033.5 Pa = 79,033.5 N/m² = 79.0335 kPa
Pext = 0.28 atm = 28,371 Pa = 28,371 N/m² = 28.371 kPa
Awin = 95 cm x 56 cm = 5,320 cm² = 0.523 m²
Differential pressure = 79,033.5 Pa - 28,371 Pa = 50,662.5 Pa = 50,662.5 N/m² = 50.6625 kPa
F = force
P = pressure
A = area
P = F/A
50,662.5 N/m² = F/0.523 m²
F = (50,662.5 N/m²)(0.523 m²)
F = 26,496.5 N ≈ 26.5 kN ANSWER