Calculating checkbox on checking the preset value

[Tinsu25800928bb1x]

Hi I am very new with Javascript

Kindly need your support i have 4 check box options which the value is set for each check boxes 

once checking the checkbox the value for the same should shown in the textbox.

Also if they checked two checkboxes the value for the same should calculate below.

[Tinsu25800928bb1x]

Laptop  Check Box 1               Value 50$

Mobile Check Box 2                 Value 25$

Desktop Checkbox 3                  Value 20$

On clicking the checkboxes the value should shown below. However, even they can select the all three check boxes which needs to be calculated below.

Charges for checkboxes (                      )

[Tinsu25800928bb1x]

[try67]

Apply those prices as the export values of the check-boxes (just as numbers) and then you'll be able to use the built-in Sum option under the Calculate tab of the text field to sum them all up.