If i sent one message every 2 minutes, how long would it take me to send 100 messages (and what formula could i use to solve future problems like this? )

Jody bought 20 shares of amazon at the close price of $121.00. she bought 20 more shares a year later at the price of $127.00. two years later, she sold all of her shares at the price of $133.00. her broker charges $50 for each transaction. after all of these transactions, how much money did jody make?