In interval estimation, the t distribution is applicable only when a. the population has a mean of less than 30. b. the sample standard deviation (s) is given instead of the population standard deviation (σ). c. the variance of the population is known. d. the standard deviation of the population is known. e. we will always use the t distribution

the forst and 3rd

step-by-step explanation:

i think the answer would be c

$113.42

i hope that is right.

step-by-step explanation:

step-by-step explanation:

we have

using a graphing tool

see the attached figure

this is a quadratic equation (vertical parabola) open up

the vertex is a > vertex

the domain of the function is all real > interval (-∞,∞)

the range of the function is the > [-6.125,∞)

the function has two x->   and

the function is increasing over the > (0.25,∞)

the function is decreasing over the > (-∞,0.25)