Let ( n ) be an even integer and let ( k ) be an integer with ( 1 ≤ k ≤ n ). Consider ( k )-element subsets of the set ( 1, 2, 3, ..., n ). How many such subsets contain at least two even numbers?
a) ( 2ⁿ⁻¹ - n )
b) ( 2ⁿ⁻¹ )
c) ( 2ⁿ⁻² - n )
d) ( 2ⁿ⁻² )
