6. An oil tank is being drained for cleaning. After t minutes there are I litres of oil left in the tank, where V(!) = 40(20 - 1) , 0 SS 20. Determine the rate of change of volume at the time t = 10. . -800 litres/minute . -400 litres/minute b. -600 litres/minute d. -200 litres/minute 7. Determine lim 3x + x2. x - -2 a. 10 C. 6 b. -2 d. -4 8. Determine lim 5. x-+ 4 a. 4 C. 5 b. -4 d. -5 9. Which of the following must be equal to lim f(x) so that the limit exists at the point with x- x-+ 3 coordinate 3? a. lim A(x) x -+ 3 b. A(3) c. 0 d. Nothing else. The one limit is sufficient. 10. Determine lim x- x2 + x3. x - 15 a. 3165 . -3165 b. 1356 d. -1356