Assume that a force acting on an object is given by {vec F} =ax{hat i} +by{hat j} , where the constants a = 3.3 {rm N/m} and b = 4.2 {rm N/m}.Determine the work done on the object by this force as it moves in a straight line from the origin to {vec r} = (12.0{hat i} + 20.0{hat j}){rm m}.