The graph shows the calling charges of two cell phone companies. At how many minutes do the two companies charge the same amount?
y
20
Charges (dollars)
8-
18
16
79
cell phone
company A
14
12
10
cell phone
company B
6
x
+
10 20 30 40 50 60 70 80
OA 0
OB.
15
20
OC. 20
0 0
40
40
Time (minutes)