Suppose that the username of myITU system must satisfy the following requirements: (i) each username must be eight to twelve characters long; (ii) each character in the username must be a letter (a-z or A-Z) or a digit (0−9); and (iii) each username must contain at least one digit (0−9). (iv) each username must start with a letter (a-z or A-Z). How many possible usernames are there for myITU system? Provide your argument to support your answer