A conducting sphere A of radius ‘a’  with charge Q, is placed concentrically inside a conducting shell  B of radius ‘b’. The sphere B is earthed. ‘C’  is the common center of  A and B. Study the following statements.

i. The potential at a distance r  from  C, where r<a is zero.
ii. The Potential difference between  A and  B is $\frac{1}{4\text{π}{\epsilon }_0}Q\left(\frac{1}{a}-\frac{1}{b}\right)$
iii. The potential at a distance r from C, where  $a\le r\le b\text{\hspace{0.17em} is\hspace{0.17em}}\frac{1}{4\text{π}{\epsilon }_0}Q\left(\frac{1}{r}-\frac{1}{b}\right)$
Which of the above statements are correct?