Question: What is the total number of Year of Intro(s), when Country of Origin is Soviet Union, when Type is Reusable, when Primary Cartridge is 40mm, and when Name/ Designation is RPG-29?
SQL: SELECT COUNT(year_of_intro) FROM table_name_87 WHERE country_of_origin = "soviet union" AND type = "reusable" AND primary_cartridge = "40mm" AND name__designation = "rpg-29"