A company is studying the effectiveness of their text message advertisements by counting the number of visits to their website that originate from a link in one of the texts. The function A(r) gives how many thousands of site visits were generated, where r is the number of text messages sent in hundreds of thousands. (part a - 5 pts) Identify the input variable of the function and describe in words what the variable represents in this model. Be detailed and include units. (part b - 5 pts) Identify the output variable of the function and describe in words what the variable represents in this model. Be detailed and include units. (part c - 4 pts) = Write a sentence to interpret A(6) 38.7 in the context of this model. (Your sentence should be about the text message advertisements and should not include words such as input, output, plug in, function, etc.).