Tính nhanh

tính nhanh:$$$\frac{2001\times 2003\times 2003\times 2005}{2003\times 4006} b, \frac{7\times 9\times 6\times 5}{12\times 5\times 9\times 3} c, \frac{8\times 9\times 3\times 24}{18\times 4\times 12}$