Figure 5-42 shows an overhead view of a 0.0250 kg lemon half and two of the three horizontal forces...

Figure 5-42 shows an overhead view of a 0.0250 kg lemon half and two of the three horizontal forces that act on it as it is on a frictionless table. Force  has a magnitude of 6.00 N and is at θ₁=30.0°. Force has a magnitude of 7.00 N and is at θ₂=30.0°. In unit-vector notation, what is the third force if the lemon half (u) is station at!, (b) has constant velocity  =  m/s, and (c) has varying velocity  = m/s²,where r is time?