The code contains 4 letters and 3 numbers
Number of ways to select a letter = 26
So, number of ways to select 4 letters = 26 x 26 x 26 x 26 = 26⁴
Number of ways to select a number = 6
So, number of ways to select 3 numbers = 6³
Number of key code combinations = 26⁴ x 6³ = 98706816
So, option C is the correct answer