A reflection grating spectrograph with a 0.2 mm by 4.0 mm slit is at the focal plane of a 4.0-meter diameter telescope. a) What is the focal length of the telescope if this slit has a size of 1.0 arcsec by 20.0 arcsec on the plane of the sky? Note: A slit width of 1 arcsec would be well matched to 1 arcsec "seeing" conditions for optimum light throughput.