Answer both questions (a) and (b), regarding to OpenGL. Please explain your reasoning and show your work:

Question 1 (6 marks) This question is about the callback functions in OpenGL. (a) (2 marks) What is the main purpose of installing various callback functions in OpenGL? (6) (4 marks) In order to achieve animation in OpenGL, there are two important functions called glutSwapBuffers and glutPostRedisplay we need to use. Usually where in your code is glutSwapBuffer placed? Where is the main purpose of glutPostRedisplay