The correct order of iron-ore mines from south-west to north-east is:
- Kudremukh (iv) – located in the south-western part of India, in Karnataka.
- Ballari (iii) – located to the north-east of Kudremukh, also in Karnataka.
- Bailadila (i) – located further north in Chhattisgarh.
- Mayurbhanj (ii) – located in the north-eastern part, in Odisha.
Hence, the correct sequence is (iv), (iii), (i), and (ii), which corresponds to option (C).

Standard electrode potential for \( \text{Sn}^{4+}/\text{Sn}^{2+} \) couple is +0.15 V and that for the \( \text{Cr}^{3+}/\text{Cr} \) couple is -0.74 V. The two couples in their standard states are connected to make a cell. The cell potential will be:
To calculate the cell potential (\( E^\circ_{\text{cell}} \)), we use the standard electrode potentials of the given redox couples.
Given data:
\( E^\circ_{\text{Sn}^{4+}/\text{Sn}^{2+}} = +0.15V \)
\( E^\circ_{\text{Cr}^{3+}/\text{Cr}} = -0.74V \)
A carpenter needs to make a wooden cuboidal box, closed from all sides, which has a square base and fixed volume. Since he is short of the paint required to paint the box on completion, he wants the surface area to be minimum.
On the basis of the above information, answer the following questions :
Find a relation between \( x \) and \( y \) such that the surface area \( S \) is minimum.