Arrange three displacement vectors, of magnitudes \(2 \mathrm{~m}\), \(5 \mathrm{~m}\), and \(7 \mathrm{~m}\), so that their sum is \((a)(+10 \mathrm{~m}) \hat{\imath}\), (b) \((-4 \mathrm{~m}) \hat{i}\), and (c) 0.