Question 712634
a) There are 10^3 = <font color="red">1000</font> different access codes.


b) The probability of selecting the correct access code is 1/1000 = <font color="red">0.001</font> which is a 0.1% chance. The probability is small, but not small enough to make me safe (I would add more digits to make it safer). Basically, if 1000 people randomly picked a code to break in, then one would break in eventually. So if this is in a densely populated area, then the chances of break in would be much higher. This is why more digits are needed.