Write a Python program using Python 3.6.2. The program should be written in the Script not Shell and it should be saved as a .py file. The program should include the following three things:

1. Using turtle graphics, draw an equilateral triangle, a square and a regular pentagon, each with side length 100.

2. Using turtle graphics, draw four concentric circles of radius 50, 100, 150 and 200.

3. Using the Python math module, compute and print out the values of a. 100! b. the log (base 2) of 1,000,000 c. the greatest common denominator of 63 and 49