Monday, 3/1/2021 (10:02 am, PT) <--- EXPIRATION DAY
sell -1 March 1, 2021 3870 put at $1.45 (prob ITM 14.30%)
buy +1 March 1, 2021 3835 put at $0.25 (prob ITM 2.31%)
net credit: $1.20 x 1 x 100 = $120 (max profit)
margin: 3361
SPX at 3893
Monday, 3/1/2021 (12:52 pm, PT) <--- almost 3 hours later
buy back 3870 short put at $0.05
NET PROFIT: $112.11 (in about 3 hours)
ROC: 3.33% (in about 3 hours) = 1217% (annualized)