c
(c) From figure, \(\overrightarrow {OA} = 0\;\overrightarrow i + 30\;\overrightarrow j \), \(\overrightarrow {AB} = 20\;\overrightarrow i + 0\;\overrightarrow j \)

\(\overrightarrow {BC} = - 30\sqrt 2 \;cos{45^o}\overrightarrow i \)\( - 30\sqrt 2 \;\sin {\rm{4}}{{\rm{5}}^{\rm{o}}}\overrightarrow j \) \( = - 30\;\overrightarrow i - 30\;\overrightarrow j \)

Net displacement, \(\overrightarrow {OC} = \overrightarrow {OA} + \overrightarrow {AB} + \overrightarrow {BC} \)\( = - 10\;\overrightarrow i + 0\;\overrightarrow j \)
\(|\overrightarrow {OC} |\; = 10\;m.\)