CAT Exam Model Paper 8 with solutions for free online practice

Let the three roots be a, b, c.
Then a + b + c = 10. Since the sum of the three prime numbers is even, one of them has to be 2. So the three roots have to be 2, 3, 5 as every other combination would give a value greater than 10.
If we cross check using ab + bc + ac = 6 + 15 + 10 = 31, it is consistent with the value in the equation (i.e. the value of c/a).
Hence, K = abc = 30.