The sodium-potassium pump makes the cell interior more by pumping sodium ions out of the cell for every potassium ions pumped in.

The sodium potassium pump helps in maintaining the acid-base balance of the body and helps in proper kidney function. It also functions to maintain the electrical charge within the cell. The sodium and potassium ions are transported inside and outside of the to maintain the proper balance ions inside the cells. This pump makes the cell interior more negative by pumping three sodium atoms out of the cell and two potassium ions going inside the cell.

500 is what you already have if it grows 2.75% a month you multiply it by the month and add it to 500

500+2.75%m