Let \(\left(B_{t}ight)_{t \geqslant 0}\) be a \(\mathrm{BM}^{1}\) and denote by \(\tau_{b}=\inf \left\{s \geqslant 0: B_{s}=bight\}\) the first time when \(B_{t}\) reaches \(b \in \mathbb{R}\). Show that

a) \(\tau_{b} \sim \tau_{-b}\);

b) \(\tau_{c b} \sim c^{2} \tau_{b}, c \in \mathbb{R}\);

c) if \(0