1. Write code that uses turtle graphics to draw four concentric circles of radius 50, 100, 150 and 200.

2. This question practices the use of a list method. Assign to the variable grades a list of 10 letter grades from among 'A', 'B', 'C', 'D', and 'F'. For example:

grades = ['A', 'F', 'C', 'F', 'A', 'B', 'A', 'C', 'A', 'B']

Write a Python expression that creates a list named frequency, in which the elements are the number of times each of the letters A, B, C, D and F appear in grades. For example, for the above value of grades, the following would be correct output: frequency = [4, 2, 2, 0, 2]