A cell phone company charges by the minute (and partial minute) for making phone calls. Arionna’s plan includes 300 minutes in the 20 dollars monthly base cost. If she uses more than 300 minutes in a month, there is a 5 dollars overage fee and an additional charge of 0 point 2 5 dollars per minute. Which graph represents the monthly cost, y , in dollars for making x minutes of calls?
Answer
A
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from negative 50 to 500 in increments of 50. The y axis ranges from negative 50 to 50 in increments of 10. The graph is comprised of 2 lines. The first line starts from the closed circle (0 comma 0) and goes to (300 comma 0). The second line starts from the closed circle (300 comma 0) and goes to (400 comma 25).
B
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from negative 50 to 500 in increments of 50. The y axis ranges from negative 50 to 50 in increments of 10. The graph is comprised of 2 lines. The first line starts from the closed circle (0 comma 0) and goes to (300 comma 20). The second line starts from the open circle (300 comma 25) and goes to (400 comma 50).
C
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from negative 50 to 500 in increments of 50. The y axis ranges from negative 50 to 50 in increments of 10. The graph is comprised of 2 lines. The first line starts from the closed circle (0 comma 20) and goes to (300 comma 20). The second line starts from the open circle (300 comma 25) and goes to (400 comma 50).
D
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from negative 50 to 500 in increments of 50. The y axis ranges from negative 50 to 50 in increments of 10. The graph is comprised of 2 lines. The first line starts from the open circle (300 comma 20) and goes to (0 comma 20). The second line starts from the open circle (300 comma 20) and goes to (400 comma 50).
Explanation
The monthly base cost is $20 for up to 300 minutes, so the graph stays horizontal at y = 20 through x = 300. Once usage exceeds 300 minutes, the $5 overage fee raises the cost to $25, and each additional minute adds $0.25; for example, at 400 minutes the cost is $20 + $5 + (100 × $0.25) = $50. Choice B shows the $20 base-cost segment and the higher-cost segment beginning just above 300 minutes.
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