Context: CREATE TABLE table_12983929_1 (total_power VARCHAR, construction_start VARCHAR, commercial_operation VARCHAR)
Question: How many different values of total power are there for the unit whose construction started on 01.03.1977 and whose commercial operation started on 01.02.1984?
Answer: SELECT COUNT(total_power) FROM table_12983929_1 WHERE construction_start = "01.03.1977" AND commercial_operation = "01.02.1984"