Okay.
3/4 of one min = 45 sec.
4/5 of one minute =48 sec.
To get Tim's count per minute, divide 30 by 45 (for count per second), then multiply by 60. For one minute, Tim can type 40 words.
Justin - (32/48)*60. Justin can also type 40 words per minute.
Multiply both word counts by five (five minutes) then add them together. 200+200=400. Your answer is 400.