LIS 2600 Week 5 the muddist point

1, why TIFF is better than PNG in black and white images, especially text and drawing? Is it GIF good at text and drawings? And in the class, we are told that PNG only use one compression, so what compression does PNG use?

2, why the information on PPT page 53 and page 54 about NTSC is different? PPT 53, " 60 "interlaced" half-frames/sec, 512x486", but page 54, "640x480 and 30 frames per second". The number of frames per second is different.

3, what about the video format extension". rmvb". It is a very popular video formats when we download videos from internet.