The velocity of an fly is given as a function of time, v(t) = (2t + 3)i + 3t 2j + (6t + 1)k (measured in m/s) The function is valid for 1 s < t < 5 s. a) (1 mark) Find an expression for the acceleration as a function of time a(t). b) (1 mark) Determine an expression for the displacement as a function of time r(t). c) (3 marks) If the object is located at r = 2i + 8j + 13k (m) at t = 3s, determine an expression for the position as a function of time r(t). d) (2 marks) Does the fly ever stop moving? Explain. e) (6 marks) At what time(s) is the fly's speed 4 m/s