28. The displacement of an object attached to the end of a spring can be modelled by the function h() = 2.4cos 121+ 7, where h is the height of the object from the floor, in centimetres, and t is the time, in seconds. Determine the acceleration of the object at time t. (3 marks) Part 4: Application [12 marks] 29. Find the equation of the tangent to the curve y = 4x - tanx at the point where x = 4 . [6 marks] 30. The population of a bacterial culture was 5000 bacteria after 15 min and 40 000 bacteria after 1 h. a) After how many minutes will the population reach 150 000 bacteria? (3 marks) b) Find the rate of growth after 15 min. Express your answer as bacteria per hour