Lucky’s 1-minute work is:
\[ \frac{1}{15} \]
\[ 10 \times \frac{1}{15} = \frac{10}{15} = \frac{2}{3} \]
\[ 1 - \frac{2}{3} = \frac{1}{3} \]
Bali’s 1-minute work is:
\[ \frac{1}{18} \]
\[ \frac{1}{3} \div \frac{1}{18} = \frac{1}{3} \times 18 = 6 \text{ minutes} \]
Thus, the correct answer is 6 minutes (Option C).