In the attachement, there is what I came up with so far. I think that finding 'a' is non-trivial, if possible at all.
- the area of a circle
- the area of a circular segment
There are
ways of drawing a 4-card hand, where

is the so-called binomial coefficient.
There are 13 different card values, of which we want the hand to represent 4 values, so there are
ways of meeting this requirement.
For each card value, there are 4 choices of suit, of which we only pick 1, so there are
ways of picking a card of any given value. We draw 4 cards from the deck, so there are
possible hands in which each card has a different value.
Then there are
total hands in which all 4 cards have distinct values, and the probability of drawing such a hand is

Answer:
The answer is 1
Step-by-step explanation:
-50+50=1