Before calcualting the probability we can identify the number of ways that you can get different numbers of head (Or let us calculate the umber of events).

There are 5 ways,

1) Zero heads out of 4 coins, the number of ways you can get this is given by,

         4C0 = 4!/(0!4!) = 1

2) Only one head

         4C1 = 4!/(1!3!) = 4

3) Only two heads

         4C1 = 4!/(2!2!) = 6

4) Only three heads

         4C1 = 4!/(3!1!) = 4

5) All four heads

         4C4 = 4!/(4!0!) = 1

Therefore the total number of events that can happen is, T,

T = 1+4+6+4+1

T = 16

Therefore the probability of not getting 3 or 4 heads

 = Number of events below three heads / Total number of events

 = (1+4+6)/16

 = 11/16

 = 0.6875

Therefore, there is a 0.6875 chance of kujain winning the game.