A function assigns the values. If Mary uses the given carrier then she can talk for 26.5 minutes.
What is a Function?
A function assigns the value of each element of one set to the other specific element of another set.
Given that the telephone long-distance carrier charges customers $0.99 for the first 20 minutes and then $0.07 for each minute ( or any part thereof) beyond 20 mins. Therefore, the function to calculate the total cost can be written as,
Total cost = Fixed cost of $0.99 + Variable cost of $0.07 for each minute
y = 0.99 + 0.77x
where x represents the number of minutes after the ter first 20 minutes.
Now, since Mary only has $6, therefore, the number of minutes Mary can talk above 20 minutes is,
6 = 0.99 + 0.77x
6 - 0.99 = 0.77x
5.01 = 0.77x
x = 6.5
Therefore, For $6 Mary can talk for 26.5 minutes, (20+6.5).
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