The correct answer to question (b) is the displacement of the particle in the fifth second is s(5) - s(4), where s(t) =- + 2t. So, s(4) = - + 2*4 = -18.6667 m (rounded), s(5) = - + 2*5 = -23.3333 m (rounded), and the displacement in the fifth second is s(5) - s(4) = -23.3333 - (-18.6667) = -4.6666 m (rounded). ANSWER to (b) is -4.6667 m (rounded).