Number of days: 20 ltbr. Daily Expenses: 1 Azkaban Unit per day
Maximum cash he can have at any time: 4 Azkaban Units
Daily Exhange rate:

Igor hopes that Viktor will solve the puzzles before he returns from Azkaban and he prom- ises to train Viktor with more challenging puzzles ahead.You have to report the sum of the product of digits in the OMR sheet i.e if minimum expenditure is 26, report your answer as `3 ( 2 xx 6 = 12 rArr 1+2 = 3)`

Explanation

`{:(56,rArr,3),(39,rArr, 9):}`
Best possible way is hit and trial while using logic.