Question $6(1$ point$)$

Forces of $2\mathrm{.}4$ N and $1\mathrm{.}8$ N act on an object at right angles to one another. What is the magnitude of a third force acting on the same object so that it remains stationary?

a$)4\mathrm{.}2$ N

b$)9\mathrm{.}0$ N

c$)3\mathrm{.}0$ N

d$)2\mathrm{.}7$ N