Solution
= Solution
For $\Gamma\subseteq\widehat G$ and $\rho>0$, the <Bohr set> is
$$
B(\Gamma,\rho)
=\{x\in G:|\gamma(x)-1|\leq\rho\text{ for every }\gamma\in\Gamma\}.
$$
Writing $d=|\Gamma|$, the <lower bound for the size of a Bohr set> is
$$
|B(\Gamma,\rho)|\geq
\left(\frac{\rho}{8}\right)^d|G|.
$$