Answer: Payback time = 0.0075
Explanation: Since payback time is calculated as:
payback time = ![\frac{installation cost}{annual savings}](https://tex.z-dn.net/?f=%5Cfrac%7Binstallation%20cost%7D%7Bannual%20savings%7D)
First determine the installation cost:
100 mm thick insulation covers 8.3 m². Then 300 mm covers 24.9 m².
To cover 8.3m² costs £20. Then, the cost to cover 24.9 m² is:
cost = ![\frac{20*24.9}{8.3}](https://tex.z-dn.net/?f=%5Cfrac%7B20%2A24.9%7D%7B8.3%7D)
cost = £60
The cost of putting the insulation is £120, so the total cost is:
total cost = £60 + £120
total cost = £180
Savings per year per 100 mm thick is £80. For 300 mm, the value of annual savings is:
savings = ![\frac{300*80}{100}](https://tex.z-dn.net/?f=%5Cfrac%7B300%2A80%7D%7B100%7D)
savings = 240
payback time = ![\frac{installation cost}{annual savings}](https://tex.z-dn.net/?f=%5Cfrac%7Binstallation%20cost%7D%7Bannual%20savings%7D)
payback time = ![\frac{180}{240}](https://tex.z-dn.net/?f=%5Cfrac%7B180%7D%7B240%7D)
payback time = 0.75
Answer:
Ionization energy tends to increase across a period because the nuclear pull is increasing while shielding is not changing because electrons are in the same energy level. Not only that as we move across a period elements are closer to a full octet.
Explanation: