To express the monthly cost \( C \) in terms of minutes of call time \( m \), we can formulate the cost as follows:
- Monthly access fee: $12.90
- Cost per minute of calling time: $0.11 per minute
Therefore, the total monthly cost \( C \) can be expressed as:
\[ C = 12.90 + 0.11m \]
where \( m \) is the number of minutes used.
Now, to find the monthly cost if you make 225 minutes of calls, we can substitute \( m = 225 \) into the cost equation:
\[ C = 12.90 + 0.11 \times 225 \]
Calculating the second term:
\[ 0.11 \times 225 = 24.75 \]
Now, adding this to the monthly access fee:
\[ C = 12.90 + 24.75 = 37.65 \]
Thus, the monthly cost if you make 225 minutes of calls this month will be $37.65.
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