The correct answer is option b) 21
explaination ::
Let a = 2k + 1, b = 2l + 1, c = 2m + 1
where k, l, m are whole number
a + b + c = 13
2k + 1 + 2l + 1 + 2z + 1 = 13
or, x + y + z = 5
The number of integrals solutions
\(=^{5+3-1}C_{3-1}=^7C_2\)
\(={7.6\over 1.2}=21\)