If a, b, c are positive real numbers such that a + b + c = 1 then the least value of (1+a)(1+b)(1+c)(1−a)(1−b)(1−c) is is
16
8
4
5
a = 1 - b - c
⇒ 1+a=(1−b)+(1−c)≥2√(1−b)(1−c)∴ (1+a)(1+b)(1+c)≥8(1−a)(1−b)(1−c)