Answer: LED have the lowest cost of operation.
Explanation:
If we ignore the initial procurement cost of the items the operational cost of any device consuming electricity is given by

Among the three item's LED consumes the lowest power to give the same level of brightness as compared to the other 2 item's thus LED's shall have the lowest operational cost.
Answer:
The nail exerts a force of 573.88 Pounds on the Hammer in positive j direction.
Explanation:
Since we know that the force is the rate at which the momentum of an object changes.
Mathematically 
The momentum of any body is defines as 
In the above problem we see that the moumentum of the hammer is reduced to zero in 0.023 seconds thus the force on the hammer is calculated using the above relations as


Android provides a huge set of 2D-drawing APIs that allow you to create graphics.
Android has got visually appealing graphics and mind blowing animations.
The Android framework provides a rich set of powerful APIS for applying animation to UI elements and graphics as well as drawing custom 2D and 3D graphics.
<h3>Three Animation Systems Used In Android Applications:-</h3>
1. Property Animation
2. View Animation
3. Drawable Animation
Answer: A is the answer, The use of headings in boldface type leads the reader to specific information.
Explanation: