#1
[tex]\\ \sf\longmapsto F_{net}=15+10-5=25-5=\vec{20N}[/tex]
#2
[tex]\\ \sf\longmapsto F_{net}=12-4-4=12-8=4N\uparrow[/tex]
#3
[tex]\\ \sf\longmapsto F_{net}=8+6-10=16-10=6N\uparrow [/tex]
They can lift the box.
#4
[tex]\\ \sf\longmapsto F_{net}=6-4=\vec{2N}[/tex]
