Suppose that 15 percent of the families in a certain community have no children, 20 percent have 1 child, 35 percent have 2 children, and 30 percent have 3. suppose further that in each family each child is equally likely (independently) to be a boy or a girl. if a family is chosen at random from this community, what is the joint probability mass function? (let b= the number of boys, and g= the number of girls, in this family)