In each of the given number-clusters, the number on the right side of = (the equal to sign) is calculated by performing certain mathematical operations on the three numbers on the left of = (the equal to sign). All three number-clusters follow the same pattern. Select the number from among the given options that can replace the question mark (?) in the third number-cluster.
27, 3, 9 = 9
64, 4, 16 = 16
15, 5, 25 = ?
1
25
2
3
3
10
4
5