A thief is upto an electornic lock with 10 digit keypad and he notices that all but three of the keys are covered in dust while the 2,4,6, and 8 keys shows considerable wear. He this can satisfy assume that the 4 digit code that opens the door must be made up of these number in some order. What is thr worst case number of combinations he must now test to try to open this lock using brute force attack?