Answer:
 5.61×10^8 ton/day
Step-by-step explanation:
 (2.08×10^5 ft³/s)·(8.64×10^4 s/day)·(6.24×10^1 lb/ft³)/(2×10^3 lb/ton)
 = (2.08·8.64·6.24/2)×10^(5+4+1-3) ton/day
 ≈ 56.07×10^7 ton/day
 ≈ 5.61×10^8 ton/day
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We have expressed the answer using 3 significant digits, to match the precision of the rate and weight.