Answer:
Hence, the probability is:
0.70
Explanation:
Let x be the total cell phones.
Let A denote the event of cell phone will receive a favorable report.
B denote the event that the cell phone is launched successfully.
Now we have to find the probability:
P(A|B)
We know that P(A|B) is calculated as:

Now it is given that:
40% of its cell phones have launched successfully.
i.e.

( Since,

Also,
In the past, 70% of successful cell phones and 20% of unsuccessful cell phones received favorable reports.
So, Number of successfully launched+favorable cell phones is successful are:
40% of 70% of the total cell phones.
i.e.

Hence, the probability P(A|B) is:
[/tex]
Hence, the probability is:
0.70