Answer :
A: y = 60 + 0.10x
B: y = 100 + 0.05x
y = total cost, x = minutes
60 + 0.10x = 100 + 0.05x
0.10x = 40 + 0.05x
40 = 0.05x
x = 800 minutes
B: y = 100 + 0.05x
y = total cost, x = minutes
60 + 0.10x = 100 + 0.05x
0.10x = 40 + 0.05x
40 = 0.05x
x = 800 minutes