Let $I_r= \int dz/(z(z-1)(z-2))$ along $C_r$, where $C_r = \{z\in\mathbb C : |z|=r\}$, $r>0$. Then
a. $I_r= 2\pi i$ if $r\in (2,3)$
b. $I_r= 1/2$ if $r\in (0,1)$
c. $I_r= -2\pi i$ if $r\in (1,2)$
d. $I_r= 0$ if $r>3$.
I am stuck on this problem . Can anyone help me please?
all options are looking wrong by using residue theorem......