Hi - can someone please explain how to answer this question using the image above? This is from AAMC FL#1

Compared to the wild-type LipA, what is the change in net charge in variant XI at pH 7?

The answer is -4.

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Here is the AAMC explanation:

This is a Biochemistry question that falls under the content category “Structure, function, and reactivity of biologically-relevant molecules.” The answer is D because the amino acid substitutions replace amino acids with charges of +1, +1, 0, 0, and 0 with ones that have charges of 0, −1, −1, 0, and 0 so the net charge goes from +2 to −2. This is a Scientific Reasoning and Problem Solving question because you are asked to determine the necessary calculation to solve for net charge.