On call = 3.5 hours:$10 Talk Time = 1/2 hour: $1.25 Wich company offers the best deal? explain your answer

If this is asking which company is cheaper then that would be talk time because 1/2 an hour costs $1.25 so if you double that it's 2.50 then double that and you get 5.00. Add 2.50 one more time and you get 7.50 then add 1.25 and you get 8.75. In the end talk time will be cheaper by $1.25