Consider two force vectors:

F$1$F$2==(2\mathrm{.}93$N$)$i$^+(5\mathrm{.}62$N$)$j$^+(2\mathrm{.}83$N$)$k$^(3\mathrm{.}24$N$)$i$^+(4\mathrm{.}39$N$)$j$^+$ak$^$

What should be the value of a$,$ in newtons, so that the two forces are perpendicular