1. The grades of 20 high school students in Mathematics are 75, . 77, 80, 81, 81, 93, 85, 77, 78, 85, 78, 94, 85, 90, 93, 93, 95, 96, 97, .' 96, with the respectively weights 1.1, 1.2, 1.5, 1.6, 1.6, 1.8, 1.7, 1.2, .' 1.3, 1.7, 1.3, 1.8, 1.7, 1.8, 1.8, 1.8, 1.9, 1.9, 1.9,and 1.9. Find the mean, weighted mean, median and mode. '- 2. The age of 15 students in Mathematics class are 15, 15, 16, 17, 18, 16, 17, 19, 19, 18, 20, 20, 20, 15, 19. Find the mean, median and mode