∵ No. of pages typed by the typist A in 4 hours = 100 x 4/10 = 40
∴ No. of remaining pages = 100 - 40 = 60
Let B and C worked for H hours
∵ (100 x H)/20 + (100 x H)/25 = 60
⇒ 5H + 4H = 60
∴ H = 60/9 = 20/3 hours = 6 hours 40 min
∴ The time at which the report was typed 03.40 p.m.