The number of triplets $( a , b , c )$ of integers such that $a < b < c$ and $a , b , c$ are sides of a triangle with perimeter 21 is (a) 7 . (B) 8. (C) 11 . (D) 12 .
The number of triplets $( a , b , c )$ of integers such that $a < b < c$ and $a , b , c$ are sides of a triangle with perimeter 21 is\\
(a) 7 .\\
(B) 8.\\
(C) 11 .\\
(D) 12 .