If in the expansion of `(x^4-1/(x^3))^(15),\ x^(-17)` occurs in rth term, then a. `r=10` b. `r=11` c. `r=12` d. `r=13`

Explanation

To solve the problem, we need to find the value of \( r \) such that \( x^{-17} \) occurs in the \( r \)-th term of the expansion of \( (x^4 - \frac{1}{x^3})^{15} \).

### Step-by-Step Solution:

1. **Identify the General Term**:
The general term \( T_{r+1} \) in the expansion of \( (a + b)^n \) is given by:
\[
T_{r+1} = \binom{n}{r} a^{n-r} b^r
...