Dr. Pepper-
First of all, nebuch.
What happened at the end?
A 4% chance is 1 out of 25.
25 * 25 is 625.
Of the 625 possible combinations:
– 24 are boy non-carrier, girl carrier
– 24 are girl non-carrier, boy carrier
– 1 is both non-carrier
– the remaining combinations are that both are carriers
The answer is 49/625 (or 7.84%) that they are compatible. Not the best odds, but IMHO probably worth $1,000 if they were about to get engaged.
There must be a more elegant solution.