findPos() {
        const i = Math.floor((simulationArea.mouseX - this.x + 35) / 20);
        const j = Math.floor((simulationArea.mouseY - this.y + 35) / 16);
        if (i < 0 || j < 0 || i > 3 || j > 3) return undefined;
        return j * 4 + i;
    }
@memberof Rom
function to find position of the index of part of rom selected.
@return {number}