Answer:
Step-by-step explanation:
Use the equation
89 < 75 + 0.7*M Subtract 75 from both sides
89 - 75 < 0.7M Combine
14 < 0.7 M Divide both sides by 0.7
14/0.7 < M
20 < M
If M goes over 20 then the flat rate is cheaper.
They both equal 78 degrees because they are the same angle which means that they have the same degrees for f and e.
We're told that



where the last fact is due to the law of total probability:



so that
and
are complementary.
By definition of conditional probability, we have



We make use of the addition rule and complementary probabilities to rewrite this as


![\implies P(B)-[1-P(A\cup B)^C]=[1-P(B)]-P(A\cup B^C)](https://tex.z-dn.net/?f=%5Cimplies%20P%28B%29-%5B1-P%28A%5Ccup%20B%29%5EC%5D%3D%5B1-P%28B%29%5D-P%28A%5Ccup%20B%5EC%29)
![\implies2P(B)=2-[P(A\cup B)^C+P(A\cup B^C)]](https://tex.z-dn.net/?f=%5Cimplies2P%28B%29%3D2-%5BP%28A%5Ccup%20B%29%5EC%2BP%28A%5Ccup%20B%5EC%29%5D)
![\implies2P(B)=[1-P(A\cup B)^C]+[1-P(A\cup B^C)]](https://tex.z-dn.net/?f=%5Cimplies2P%28B%29%3D%5B1-P%28A%5Ccup%20B%29%5EC%5D%2B%5B1-P%28A%5Ccup%20B%5EC%29%5D)


By the law of total probability,


and substituting this into
gives
![2P(B)=P(A\cup B)+[P(B)-P(A\cap B)]](https://tex.z-dn.net/?f=2P%28B%29%3DP%28A%5Ccup%20B%29%2B%5BP%28B%29-P%28A%5Ccap%20B%29%5D)


10 (13) 15
35 (37) 40
45 (48) 50
60 (61) 65
90 (93) 95