The company charges 15 dollars per month for first 300 text messages and thereafter 0.08 dollars for any additional text message.
It says that we used additional 60 text messages (after fair usage of first 300 messages in the plan).
Our bill for this month would be sum of charges for 300 messages and charges for additional 60 messages.
Total bill = 15 dollars + 60x0.08 dollars = (15 + 4.80) dollars.
Total bill = 19.80 dollars.
Hence, our bill this month would be 19.80 dollars.
