The figure shows an overhead view of a 0.028 kg lemon half and two of the three horizontal forces that act on it as it is on a frictionless table. Force F 1 has a magnitude of 4 N and is at 01 = 28°. Force F 2 has a magnitude of 7 N and is at 02 = 33°. In unit-vector notation, what is the third force if the lemon half (a) is stationary, (b) has the constant velocity v = (10î - 11j) m/s, and (c) has the = (14tî - 15t j) m/s2, where t is time