$.$ If a $=(28$m$/$s$)$

x $+(11$m$/$s$)$

y and b $=(4$m$/$s$)$

x $(3$m$/$s$)$

y $,$ where $$

x is the unit vector in the x$-$direction and

$$

y is the unit vector in the y$-$direction. What is the magnitude of the vector a $-$ b$?$

a$)27\mathrm{.}8$ m$/$s b$)33\mathrm{.}0$ m$/$s c$)43\mathrm{.}0$ m$/$s d$)37\mathrm{.}8$ m$/$s e$)$ none of the above