Find the restrictions of the rational function {6x² + 13x - 63}/{3x² + 11x - 42} :
a) x ≠ -7, x ≠ {6}/{3}, x ≠ {-21}/{3}
b) x ≠ -7, x ≠ {11}/{3}, x ≠ {-14}/{3}
c) x ≠ 7, x ≠ {6}/{3}, x ≠ {-14}/{3}
d) x ≠ -7, x ≠ {13}/{3}, x ≠ {-21}/{3}