Answer:
19.24 weeks
Step-by-step explanation:
Given that;
Mean, m = 18
Standard deviation, s = 3
Break down cost = 2000
Preventive maintenance cost = 1400
The optimal preventive maintenance level is Given by :
Mean + service level * standard deviation
Service level = preventive maintenance cost / (breakdown cost + preventive maintenance cost)
Hence,
Service level = 1400/(1400+2000) = 1400 / 3400
Service level = 0.4117647
Optimal preventive maintenance level :
18 + (0.4117647 * 3)
18 + 1.2352941
= 19.235
= 19.24 weeks
3 times: Rate, Rate of change and Slope.
24 is what i believe the answer is

,

,

,

,

;; to find the answer, set the expressions equal to each other, since the sum of the numbers should be the same.
Use

and solve for

, which would result in

.
You can also use

to find

– or

.
Plug in the values for

and

, and find

using

or

and results in

.
After plugging in the

value, you can easily find

and

.

– since 66 is the sum of a full row, and the sums of the numbers in each row, column, and diagonal are the same, so therefore,

should also equal 66. This results in

, and, using the same value for the sum of

, or

, we find that

.
The final answer is

,

,

,

,

.
Sorry it took so long;; I hope this helps :)