help me graph theory

2)/2 vertices of degree 3. ( 4.19 Let T be a tree of order n and size m having ni vertices of degree i for 12 1 . Then n = ??ni and 2(n 1) 2m iin (a) Prove that 2 n+2n +3ns+ 4ns+ (b) A tree T has three vertices of degree 2, five vertices of degree 3, two vertices of degree 4 and no vertices of degree 5 or more. According to the formula in (a), how many end- vertices does T have