Derivatives

Class Name: Derivatives
Method Name: calcDerivative
Parameters: String,int,int
Returns: int

Implement a class Derivatives which contains a method calcDerivative.  The
method takes a String representing a polynomial, and two ints, k and x.  The
method returns the kth derivative of the polynomial evaluated at x.

The first derivative of any term of a polynomial is:
1st derivative of (a*x^n) = (a*n*x^(n-1)).

The first derivative of any polynomial is the sum of the first derivatives of
the polynomial's terms.
The kth derivative of a polynomial is the 1st derivative of the (k-1)th
derivative of the polynomial.
The 0th derivative of a polynomial is the polynomial itself.

The String will be of the form:
"a1*x^n1+a2*x^n2+...."
There are no spaces.
All the a's are non-negative integers less than 20
All the n's are unique non-negative integers less than 10.
The String is at most 50 characters and at least 5 characters.

Here is the method signature:
public int calcDerivative(String poly,int k,int x);

poly is of the correct form.
k is an integer between 0 and 10, inclusive.
x is an integer between -10 and 10, inclusive.

Examples:
*If poly="3*x^3+2*x^1+2*x^0", k=1, and x=1:
The first derivative is: 3*3*x^(3-1)+2*1*x^(1-1)+0*2*x^(0-1)=9*x^2+2*x^0.
The first derivative evaluated at x=1 is: 9*1^2+2*1^0=11
So the method returns 11.

*If poly="2*x^5+3*x^2", k=2, and x=-2,
The first derivative is: 5*2*x^(5-1)+3*2*x^(2-1)=10*x^4+6*x^1.
The second derivative is: 10*4*x^(4-1)+6*1*x^(1-1)=40*x^3+6*x^0.
The second derivative evaluated at x=-2 is 40*(-2)^3+6*(-2)^0=-314.
So the method returns -314.