Answer :
Here m/n be the probability of 123/392, where m is 123 and n is 392, so the m+n is 515
Here considering xⁿ to be the flipping heads of n numbers , so the generating functions for these coins are (1+x)(1+x)(3+4x) order, so the product those orders we get ,
(1+x)*(1+x)*(3+4x)= 4x^3+11^2+10x+3 ,here axⁿ means the n number of ways to get n number of head .Now the square of the sum of the coefficient is (4+11+10+3)²= 28^2 =784, and the sum of the square of each coefficient is(4²+11²+10²+3²)= 246.The probability will be: 246/784=123/392 =123+392 = 515
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