The input source supplies $I_i=V_i/R_i$ into the <virtual ground>, so the complete circuit's input resistance is $R_i$. The ideal output is a zero-resistance controlled voltage source:
$$
\boxed{R_{\rm in}=R_i,\qquad R_{\rm out}=0.}
$$
These are properties of the closed-loop circuit, distinct from the infinite input resistance of the amplifier terminals themselves.

Solution

Past exam of the physics 2 paper of the University of Oxford / 2013 / 8 / ii / Solution

 Solution (source code)