Table:
text: 1975–76 Chicago Black Hawks season
Regular season
Regular season
Date_ Visitor Score Home Record
February 11 Los Angeles Kings 7-4 Chicago Black Hawks 23–16–16
February 14 Chicago Black Hawks 5–4 Kansas City Scouts 24–16–16
February 15 Boston Bruins 4–1 Chicago Black Hawks 24–17–16
February 18 Buffalo Sabres 4–4 Chicago Black Hawks 24–17–17
February 21 Chicago Black Hawks 1–10 Pittsburgh Penguins 24–18–17
February 22 California Golden Seals 5–2 Chicago Black Hawks 24–19–17
February 24 Chicago Black Hawks 4–1 Vancouver Canucks 25–19–17
February 26 Chicago Black Hawks 6–2 Los Angeles Kings 26–19–17
February 28 Chicago Black Hawks 1–4 New York Islanders 26–20–17
February 29 Chicago Black Hawks 1–4 Washington Capitals 26–21–17
March 4 Chicago Black Hawks 4-6 Buffalo Sabres 26–22–17

text: 1975–76 Chicago Black Hawks season
Regular season
Regular season
Date_ Visitor Score Home Record
October 29 Montreal Canadiens 1–2 Chicago Black Hawks 5–4–2
November 1 Chicago Black Hawks 3–1 Detroit Red Wings 6–4–2
November 2 Vancouver Canucks 1–6 Chicago Black Hawks 7–4–2
November 5 Philadelphia Flyers 4-4 Chicago Black Hawks 7–4–3
November 8 Chicago Black Hawks 7–5 Pittsburgh Penguins 8-4–3
November 9 Minnesota North Stars 0–3 Chicago Black Hawks 9–4–3
November 12 Chicago Black Hawks 4–4 New York Rangers 9-4–4
November 13 Chicago Black Hawks 5-5 Philadelphia Flyers 9–4–5
November 15 Chicago Black Hawks 4-4 Montreal Canadiens 9–4–6
November 19 Chicago Black Hawks 4–2 Los Angeles Kings 10–4–6
November 22 Chicago Black Hawks 1–1 Vancouver Canucks 10–4–7

Question: What was the score on February 21 when the Chicago Black Hawks' home team was the Pittsburgh Penguins in the 1975-76 season?