1 answer
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First, we need to subtract the flat rate from the total monthly bill to find out how much of the bill is due to the per minute charge:
$38.44 - $3.99 = $34.45
Next, we need to divide the remaining amount by the per minute charge rate to find out how many minutes were used:
$34.45 รท $0.05 = 689 minutes
Therefore, Casey talked on her phone for 689 minutes.