A particle p moves with constant velocity v. initially p is at the point with position vector a. t seconds later p is at the point with position vector b. find v when: a) a= 2i + 3j, b= 6i + 13j, t= 2 b) a= 3i - 5j, b= 9i + 7j, t= 3 c) a= -4i + j, b= -12i - 19j, t= 4 please help !!!!