Answer:
Step-by-step explanation:
Given that the revenue reaches a maximum of about $ 59000 in April and a minimum of about $ 29000 in October. Suppose the months are numbered 1 through 12, where the months are numbered 1 through 12
Then minimum when x=10 and maximum when x = 4
Average = 44000 correspond to middle line
Amplitude = 
Hence the function roughly would be

So we found out two values for A and D
To find values for B and C
The minimum of sine function corresponds to -pi/2 here it is 10 and maximum pi/2 here is 4.
Period = 12 months
So B = coefficient of X = 
Because symmetrical about x=7 we have x-7 with a negative sign since min atx =10
