Compute the derivative $of$ the function

$f(x)=(\frac{3x^2-x+1}{x^2+1}{)}^7$

Select one:

$a.7(\frac{3x^2-x+1}{x^2+1}{)}^6$

$b.7(\frac{3x^2-x+1}{x^2+1}{)}^6*\frac{x^2+4x-1}{(x^2+1{)}^2}$

$c.7(\frac{3x^2-x+1}{x^2+1}{)}^6*\frac{1}{(x^2+1{)}^2}$

$d.$