把\(\rm{a}\) \(\rm{L}\)含\(\rm{(NH_{4})_{2}SO_{4}}\)和\(\rm{NH_{4}NO_{3}}\)的混合液分成两等份,一份用\(\rm{b}\) \(\rm{mol}\)烧碱刚好把\(\rm{NH_{3}}\)全部赶出,另一份与\(\rm{BaCl_{2}}\)溶液完全反应,消耗\(\rm{c}\) \(\rm{mol}\) \(\rm{BaCl_{2}}\),则原溶液中\(\rm{c(NO_{3}^{-})}\)为\(\rm{(}\) \(\rm{)}\)