the sum must be minimized and digits are unique, hence start with the lowest terms for tens and add on digit terms

hope this helps

The solution provided by motion2020 is precise. I'm just trying to elaborate on question

We know ten digits = ( 0,1,2,3,4,5,6,7,8,9)

Let Set S = { 0,1,2,3,4,5,6,7,8,9}

Using the above ten digits we have to form 5 numbers which are between 10 to 99 .SUCH THAT,
i) Each digit in Set S can be used only once.
ii) Sum of the 5 numbers formed should be as low as possible.

So the 5 number satisfying above condition is {10,26,37,48,59}

Now Quantity A = Greatest of the 5 numbers = 59
Quantity B = 60

Therefore Quantity A < Quantity B
Hence answer is option B