Answer: the monthly cost for 74 minutes of calls is 14.48
Step-by-step explanation:
let x represent the number of minutes for the month.
Let y represent the monthly cost for x minutes.
If we plot y on the vertical axis and x on the horizontal axis, a straight line would be formed. The slope of the straight line would be
Slope, m = (17.34 - 12.06)/(100 - 52)
m = 5.28/48 = 0.11
The equation of the straight line can be represented in the slope-intercept form, y = mx + c
Where
c = intercept
m = slope
To determine the intercept, we would substitute x = 52, y = 12.06 and m = 0.11 into y = mx + c. It becomes
12.06 = 0.11 × 52 + c = 5.72 + c
c = 12.06 - 5.72
c = 6.34
The linear function becomes
y = 0.11x + 6.34
The monthly cost for 74 minutes of calls would be
y = 0.11 × 74 + 6.34
y = 14.48
