A new incentive plan for the Talk Alot long-distance phone company varies the cost of a call

Question:

A new incentive plan for the Talk Alot long-distance phone company varies the cost of a call according to the formula cost = a + b log t, where t represents time in minutes. When calling long distance, the cost for the first minute is $0.50. The cost for 15 min is $3.44.
a. Find the a-value in the equation.
b. Find the b-value in the equation.
c. What is the x-intercept of the graph of the equation? What is the real-world meaning of the x-intercept?
d. Use your equation to predict the cost of a 30-minute call.
e. If you decide you can afford only to make a $2 call, how long can you talk?