Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[Q]: Problem: the price of a book is increased from $ 300 to $ 390. what is the % of increase in its price ?
Options: a. 10 %, b. 20 %, c. 30 %, d. 35 %, e. 45 %
[A]: c


[Q]: Problem: subtracting 3 % of a from a is equivalent to multiplying a by how much ?
Options: a. 0.97, b. 9.4, c. 0.094, d. 94, e. none
[A]: a


[Q]: Problem: lally ' s internet provider offers unlimited traffic which costs $ 0.5 per day charged off at 12 a. m. the service is discontinued when client ' s debt exceeds $ 5. if today in the morning lally makes a payment of $ 7, for how many days, including today, will she be connected to the internet without any additional payments, given her initial balance was $ 0 ?
Options: a. 15, b. 24, c. 25, d. 26, e. 13
[A]:
c