MathDB

Let

N

be the number of ways of choosing a subset of

5

distinct numbers from the set

{10a+b:1\leq a\leq 5, 1\leq b\leq 5}

where

a,b

are integers, such that no two of the selected numbers have the same units digits and no two have the same tens digit. What is the remainder when

N

is divided by

73

Problem Statement