What is the casting temperature for the alloy with hardness 21?
CREATE TABLE table_name_98 (casting_at__°c_ VARCHAR, hardness VARCHAR)
SELECT casting_at__°c_ FROM table_name_98 WHERE hardness = "21"
### Context: CREATE TABLE table_name_98 (casting_at__°c_ VARCHAR, hardness VARCHAR) ### Question: What is the casting temperature for the alloy with hardness 21? ### Answer: SELECT casting_at__°c_ FROM table_name_98 WHERE hardness = "21"