Two possiblities.
VZ, and ZV.
I think if you do 20 multiplied by 5 it would be $100
We will use the following formula to work out the confidence interval
Upper limit = μ + z* (σ/√n)
Lower limit = μ - z* (σ/√n)
We have
μ = 79.3
σ = 7.8
n = 12
z* is the z-score for 95% confidence level = 1.96
Substitute these into the formula, we have
Upper limit = 79.3 + 1.96 (7.8/√12) = 83.7
Lower limit = 79.3 - 1.96 )7.8/√12) = 74.9
Y = 42.5x + 45.....for 5 hrs.....x = 5
y = 42.5(5) + 45
y = 212.50 + 45
y = 257.50 <===
V=4.16 in this one ask if you need an explanation