In reply to tpan:
The first part without solve/before is correct. Note that the probability of
len>10 is 20/53
The second part with solve/before is not correct. There are still 53 solutions. The probability to have typ=1 and len>10 is now 1/4, or 13.25/53.
The probability of
len>10 is now (13.25 + 3*13.25 * 5/16)/53, or 25.67/53