19. (12 points) In response to the national strategy of "targeted poverty alleviation, industrial poverty alleviation," Harbin City is recruiting volunteer advocates for the "Poverty Alleviation Policy" from the public. From 500 volunteers aged between 20 and 45, 100 are randomly selected, and their age frequency distribution histogram is shown in Figure 5.
(1) Find the value of $x$ in the figure;
(2) Among the 100 selected volunteers, 10 are chosen using stratified sampling based on age to participate in the publicity campaign at the central square. Then, 3 of these 10 volunteers are selected to serve as primary leaders. Let $X$ be the number of these three volunteers who are under 35 years old. Find the distribution of $X$ and its expected value.