You order a 2 kW system of photovoltaic cells to be install on ...

[Mr.Thesaxman]

You order a 2 kW system of photovoltaic cells to be install on the roof of your house. The cells are guaranteed to last at least 25 years.
 
  The cells plus installation plus electrical equipment will cost you 20,000 if you buy now, but 10,000 if you wait ten years. The average cost of electricity from your utility is 10 cents per kilowatt hour. What else do you need to know in order to calculate the amount of money you will have spent within 25 years going with either plan? A) You need to know the average number of kilowatt-hours you consume each year.
  B) You need to know whether your utility company is willing and able to purchase any excess electricity you produce.
  C) You may need to know the cost of additional storage batteries should you need to store your excess harvested electrical energy.
  D) You may need to know all of the above.

Question 2

The number of valence electrons in sulfur is ________.
 
  A) 2
  B) 4
  C) 6
  D) 8

[vickyvicksss]

Answer to Question 1

D

Answer to Question 2

C

[Mr.Thesaxman]

TYSM

[sultansheikh]

Gracias!