The Function Graphed Is of the Form Y $$y = a \sin b x \text { or } y = a \cos b x , \text { where } b > 0$$

The function graphed is of the form y $$y = a \sin b x \text { or } y = a \cos b x , \text { where } b > 0$$ Determine the equation of the graph.
-The chart represents the amount of fuel consumed by a machine used in manufacturing. The machine is turned on at the beginning of the day, takes a certain amount of time to reach its full power (the point at which it uses the most fuel per hour) , runs for a certain number of hours, and is shut off at the end of the work day. The fuel usage per hour of the machine is represented by a periodic function. When does the machine first reach its full power?

A) After 4 hours
B) After 14 hours
C) After 2 hours
D) After 7 hours