26. Consider the eight-digit bank identification number a¡a2 . .ag, which is followed by a ninth check digit a9 chosen to satisfy the congruence a9 = 7a1 + 3az + 9az + 7a4 + 3as +9as + 7a7 +3as (mod...

Extracted text: 26. Consider the eight-digit bank identification number a¡a2 . .ag, which is followed by a ninth check digit a9 chosen to satisfy the congruence a9 = 7a1 + 3az + 9az + 7a4 + 3as +9as + 7a7 +3as (mod 10) (a) Obtain the check digits that should be appended to the two numbers 55382006 and 81372439. (b) The bank identification number 237a418538 has an illegible fourth digit. Determine the value of the obscured digit.