A 75 year old man presents with a long history of shortness of breath and ankle oedema. His serum biochemistry shows sodium 122 mmols/l and potassium of 2.9 mmols/l. He now complains of weakness.Which of the following is likely to explain the above biochemical picture? 1) Addison's Disease 2) Nephrotic syndrome 3) Primary hyperaldosteronism 4) SIADH 5) Diuretic therapy