4. The padlock on lock consists of a 5 digit code taken from the digits 01,2,3.4,5.6,7,8,9, No digits can repeat. Determine the number of possible codes under the following scenarios a) The code cannot begin with zero b) The code can begin with zero, and the code ends with on even number. 5. Ten Kindergarten students join hands in a circle (after there's a COVID vaccine) to play Ring Around the Rosie, In how many arrangements are Addy and Caleb together