Description for Correct answer:
A's and B's 1 h work = 1/10

B's and C's 1 h work = 1/15
and A's and C's 1 h work = 1/12

A's, B's and C's 1 h work = \( \Large\frac{1}{2}\left(\frac{1}{10}+\frac{1}{15}+\frac{1}{12}\right) \)
=\( \Large\frac{1}{2} \times \frac{1}{4} = \frac{1}{8} \)

Hence, B's work in 1 h = \( \Large\frac{1}{8} - \frac{1}{12} = \frac{1}{24}\)
B independently can complete the work in 24 h.