The Total Weekly Sales for a Newly Released Portable Media $$\left\{ \begin{array} { l l } S = 10 x + 70 & \text { PMP1 } \\S = - 10 x + 210 & \text { PMP2 }\end{array} \right.$$

Multiple Choice

The total weekly sales for a newly released portable media player (PMP) increased each week.At the same time,the total weekly sales for another newly released PMP decreased each week.Models that approximate the total weekly sales S (in thousands of units) for each PMP are​ $$\left\{ \begin{array} { l l } S = 10 x + 70 & \text { PMP1 } \\S = - 10 x + 210 & \text { PMP2 }\end{array} \right.$$ ​ where x represents the number of weeks each PMP was in stores,with x = 0 corresponding to the PMP sales on the day each PMP was first released in stores.After how many weeks will the sales for the two PMPs be equal?
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A) 11 weeks
B) 9 weeks
C) 7 weeks
D) 3 weeks
E) 5 weeks