(i) SP = Rs.1596 and gain = 12%

= 1425

So, Cost Price (CP) will be Rs.1425.

(ii) SP = Rs.2431 and loss = 6%

= 2600

So, Cost Price will be Rs.2600.

(iii) SP = Rs.657.60 and loss = 4%

= 685

So, Cost Price will be Rs.685.

(iv) SP = Rs.34.40 and gain = 7%

= 32

So, Cost Price (CP) will be Rs.32.