The maximum possible profit = maximum possible difference in SP and CP.
It means SP be maximum and CP be minimum
CP (min) = Rs. 399
19 x m = 399, where m is an integer.
Again SP (max) = Rs. 697, which is very close to 699
Here 697 = 17 k, k is a positive integer.
So, the maximum profit = 697 - 399 = Rs. 298