數學與統計 大學 約3年以前

請問第13題的b怎麼算 離散數學第一章 第二張是答案可以參考～

b) X, 2-3, 3i 35 ; 1< 13. In how many ways can we distribute eight identical white balls into four distinct containers so that (a) no container is left empty? (b) the fourth container has an odd number of balls in it? nansion of