Assume that a firm uses a nested dictionary to maintain the information on annual sales made from various sales strategies for 2018, 2019, and 2020.

sales_3_years = {'2018': {"Radio Sales": 5000, "TV Sales": 26000, "Direct-Mail Sales": 1000, "Telephone Sales": 26000}, '2019': {"TV Sales": 26000, "Online Sales": 37000, "Telephone Sales": 9000, "Radio Sales": 3000}, '2020': {"Telephone Sales": 8000, "TV Sales": 19000, "Online Sales": 107000}}

Write a (possibly nested) for loop to answer: How many distinct strategies have been used? What are the total sales made from them for the 3 consecutive years? Store your result in a dictionary that looks like the following (the order in which entries are listed can be different):

 {'Radio Sales': 8000, 'TV Sales': 71000, 'Direct-Mail Sales': 1000, 'Telephone Sales': 43000, 'Online Sales': 144000}

Hint: think about using dict.get()