In how many ways can Rs.16 be divided into 4 persons when none of them get less than Rs. 3?

Required number of ways= Coefficient of x16 inx3+x4+x5+…+x164= Coefficient of x16 in x121+x+x2+…+x124= Coefficient of  x4 in 1−x134(1−x)−4= Coefficient of  x4  in 1−13x5+…×1+4x+…+(r+1)(r+2)(r+3)3!xr=(4+1)(4+2)(4+3)3!=35