Teacher:In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Teacher: Now, understand the problem? Solve this instance: ['509', '2649', '7253', '4917', '3319', '6673', 't', 'l', '9921', 'v', '7877', 'W', 'W', '8451', '2751', 'P', '5477', '6109']
Student:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
509, 2649, 7253, 4917, 3319, 6673, 20, 12, 9921, 22, 7877, 23, 23, 8451, 2751, 16, 5477, 6109