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?
Schema: create table table_12983929_1 (total_power varchar, construction_start varchar, commercial_operation varchar, PRIMARY KEY (total_power))
SQL: select count(total_power) from table_12983929_1 where construction_start = "01.03.1977" and commercial_operation = "01.02.1984"