The brightness of certain stars can fluctuate over time. Suppose that the brightness of one such star is given by the following function. B() 10.5+1.9 cos 0.18r In this equation, B (r) represents the number of magnitudes of brightness, and I is the time in days. Find the following. If necessary, round to the nearest hundredth. Period of Bdays Minimum brightness: magnitudes Number of cycles of 8 per day: X F