Write a MATLAB function called FIRdesign which calculates the impulse response, [], of the causal FIR filter that minimizes the mean square error between ( ) and ( ). The function should have the form of

= FIRdesign (, , )

where h is the causal FIR filter's impulse response, wl = , wu = , and N is the length of the rectangular window sequence, [].

Here are some helpful formulas that help explain what the function is bases on: