3. Calculate the amount of work done in each situation. a. A stove is slid 3 m across the floor against a frictional force of 150 N. b. A 40 kg rock falls 40 m down a slope at an angle of 50 to the vertical. c. A wagon is pulled a distance of 250 m by a force of 140 N applied at an angle of 20 to the road. d. A lawnmower is pushed 500 m by a force of 100 N applied at an angle of 45 to the horizontal. 4. Determine each of the following by using the method shown in Example 3: a. 1x} b. -7x] c. 1Xk d. -7xk7. In Re, points A(-2, 1, 3), B(1, 0, 1), and C(2, 3, 2) form the vertices of AABC. a. By constructing position vectors AB and AC, determine the area of the triangle. b. By constructing position vectors BC and CA, determine the area of the triangle. c. What conclusion can be drawn?9. Parallelogram OBCA has its sides determined by OA = a = (4, 2, 4) and OB = b = (3, 1, 4). Its fourth vertex is point C. A line is drawn from B perpendicular to side AC of the parallelogram to intersect AC at N. Determine the length of BN