Calling multiples of 4Number Theory Level 2
Calvin wishes to make a phone call to a friend. He knows that the first 3 digits of the 7-digit phone number are 765, and the other 4 digits consists of the digits 4, 3, 2 and 1 in some order. He recalls that the phone number is a multiple of 4. How many possible telephone numbers are there, which satisfy these conditions?