Add Scientific Notation

The user can calculate the addition or the subtraction of any set of numbers in scientific notation.
Firstly, the user has to introduce the numbers in scientific notation. A number in scientific notation is useful to represent very big and very small numbers in a shorter way.
The format of the scientific notation is: a decimal number (whose absolute value is bigger or equal to 1 and smaller than 10) multiplies by a power of ten (ten raised to an integer exponent).
When the user introduces the numbers the app will do the operations. To add or subtract numbers in scientific notation, all the numbers have to have the same exponent. Therefore, we change the numbers in order to
they have the same exponent. When we have the same exponent we add or subtract the decimal numbers and we keep the same exponent.
When we have added all the numers we convert the result into scientific notation.
If the user only introduces a number the app converts this number into scientific notation.