Answer:
b
Step-by-step explanation:
Given:
n = 50, sample size

, sample mean
s = 2.4 min, sample standard deviation.
The confidence interval is

At the 99% confidence level, t* (from the student's t-distribution) is
t* = 2.68
Therefore
t*(s/√n) = 2.68*(2.4/√50) = 0.9096
The confidence interval is
(23.6-0.9096, 23.6+0.9096) ≈ (22.69, 24.51)
Answer: (22.7, 24.5)
For this case we must raise an inequality.
We have "d" dollars initially and they are spent 12. Then:

At least 51 dollars remain, then, the sign of inequality is greater or equal in favor of the expression
, that is:

Resolving:

There are at least 63 dollars left in the account.
Answer:
