Table: grand_prix_1971_2
Columns: driver
constructor
laps
time_retired
grid

Question: Who constructed the car that has a Time/Retired of engine, and over 50 laps?
SQL: SELECT "constructor" FROM grand_prix_1971_2 WHERE "time_retired" = 'engine' AND "laps" > 50

Question: What is the time/retired for ronnie peterson with under 75 laps and a grid under 15?
SQL: SELECT "time_retired" FROM grand_prix_1971_2 WHERE "laps" < 75 AND "grid" < 15 AND "driver" = 'ronnie peterson'