The following is a piece of OpenGL code for drawing a quad in a viewport: void myDisply(void) \{ gIViewport(0,0,300,200); gIMatrixMode(GL_PROJECTION); gILoadIndentity(); gIOrtho2D(-1,1,-1,1); gIBegin(GL_QUADS); gIColor3f(1,0,0); gIVertex2i(-0.5,-0.5); gIVertex2i(+0.5,-0.5); gIVertex2i(+0.5,+0.5); gIVertex2i(-0.5,+0.5); gIEnd(); a) Draw a diagram to illustrate the content generated on the screen. b) Calculate the area of the displayed quad in pixels