Calculate the energy equivalent in joules of the mass of a proton

The problem should only have one part to it, but this one has two.
Before I can do the mass/energy conversion, I have to go and
look up the proton mass for myself ... go out and collect the straw
to make my bricks, as it were.  As if the fabulous bounty of 7 points
makes it worth it.  They make us do everything around here.

OK.  In my Physics book⁽¹⁾, the proton rest mass is

                       1.67 x 10⁻²⁷  kg.

The formula that relates mass to the equivalent energy is

                        E = m c²  .

The method of applying the formula is known as "plug in what you know",
as follows:

                       E  =  (mass) x (speed of light)²

                          =  (1.67 x 10⁻²⁷ kg) x (3 x 10⁸ m/s)²

                         =  (1.67 X 10⁻²⁷ Kg) x (9 x 10¹⁶ m²/s²) 

                          =        (1.5 x 10⁻¹⁰)  (kg-m²/s²)

                          =            1.5 x 10⁻¹⁰  joule .                           


⁽¹⁾  Halliday, David and Resnick, Robert, Physics , John Wiley & Sons,
Inc., 1960,  inside front cover, "SELECTED PHYSICAL CONSTANTS".

Independent variable is something that is changed in a experiment.