I need help on how to get the sample period from this dataset to answer the following question:

Use the datasetBerkshire.csv(Links to an external site.)

with the following variables. All returns reported as a decimal (as opposed to a percentage).

Sample Period: From30thNov 1976to31stDec 2005 (Inclusive)

• Column (1):Date, Calendar Date
• Column (2):BRKret, Berkshire Hathaway's monthly return
• Column (3):MKT, the return on the aggregate stock market
• Column (4):RF, the risk free rate of return

Link to CSV: https://www.dropbox.com/s/plo0hc4t008s0xq/Berkshire.csv?dl=0

Question:

What is Berkshire Hathaway's arithmetic average return over the sample period? (Select the closest)

1.5%

1.9%

2.3%

2.7%

7.37%