Answer:
req 1)
Plan A
0.42 x 150 + 0.17 x 70 = 74.9
Plan B
0.52 x 150 + 0.15 x 70 = 88.5
Plan C $80
req 2)
from 0 to 190 minutes Plan A
from 191 and beyond Plan C
req 3)
the proportion should be 1/6 daycalls and 5/6 evenings
Explanation:
150 day calls
70 minutes evening calls
Plan A
0.42 x 150 + 0.17 x 70 = 74.9
Plan B
0.52 x 150 + 0.15 x 70 = 88.5
Plan C $80
2) A will be preferable to B as it has the lower cost
now at some point C will be better as the cost is a flat rate
80 dollars / 0.42 per minute = 190.47
3) 0.42X + 0.17Y = 0.52X + 0.15Y
a minute of daycall is 10 cent higher in plan B
while a minute of evening call is 2 cent lower
thus, to balance there was to be 5 times more evening call than day times:
1:5 1 + 5 = 6
the proportion should be 1/6 daycalls and 5/6 evenings
