Here's the formula for your original request:
switch(r, 1, 20, 2, 16, 3, 14, 4, 11, 5, 10, 6, 9, 7, 8, 8, 7, 9, 6) * n + if(n > 9, 20)
To add your "entry fee" multiplier:
(switch(r, 1, 20, 2, 16, 3, 14, 4, 11, 5, 10, 6, 9, 7, 8, 8, 7, 9, 6) * n + if(n > 9, 20)) * if(bc > 0, 1.5, 1)