During a rocket launch the cabin accelerates upward at 4.0ms−2. A helium balloon of mass 5.0g and volume 7.0×10−3m3 is released inside the cabin filled with air of density 1.2kgm−3. Assuming the mass of helium is negligible compared with the balloon mass and ignoring air resistance, determine the magnitude and direction of the balloon’s acceleration relative to the cabin immediately after release.