The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 47 minutes of calls is $14.93 and the monthly cost for 90 minutes is $20.52. What is the monthly cost for 49 minutes of calls?

a

step-by-step explanation:

u take $30 minus $24. the answer/original($30)

irst, find the z score of a score of 80. this is given by the formula z = (x-u)/o, where x is the score, u is the mean, and o is the standard deviation. this gives

z = (80-78)/12 = 1/6 = .1667

now, find what percentile a z score of 1/6 correlates to in the normal distribution.

a z score of 1/6 = .1667 is equivalent to the 56.36th percentile of the distribution. so the probability a score is over this is 1-.5636 = .4364

the mean of a sample mean is equal to the original mean. however, the standard deviation of a sample mean is equal to the original standard deviation divided by the square root of n (sample size). so the new standard deviation is 12/sqrt(16) = 3.

the new z score is 80-78/3 = 2/3 = .667. this is equivalent to the 74.86th percentile. so the probability that the mean will be greater than this score is 1-.7486 = .2514.

a.for lorena 14 hours makes $126   for 16 hours she makes 144

for julie 6 hours makes $72 for 21 hours its $252

b. julie makes more money than lorena julie makes $12 an hour and lorena makes $9  

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