$n_1, n_2, n_3, \dots, n_{10}$ are 10 numbers such that $n_1 > 0$ and the numbers are given in ascending order. How many triplets can be formed using these numbers such that in each triplet, the first number is less than the second number, and the second number is less than the third number?
- $109$
- $27$
- $36$
- None of these