Let S be the empty set. Add the elements of {1, 2} to S, and after 1 minute randomly remove 1 element of S. Next add the 4 elements of {3, 4, 5, 6} to S and after 30 sec randomly remove 2 of the 5 elements of S. Continue this process forever, each time doubling the number of elements added and removed and halving the time. To the nearest hundredth of a minute, find the average length of time 1 remains in S. 1.30 1.32 1.34 1.36 1.38