Answer: 1000 dollars
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Step-by-step explanation:
There are 1+19 = 20 people total. The prize money $70,000 is divided among those 20 people equally to get (70,000)/20 = 3500 dollars per person.
Ahmad saves $2500 of his $3500 prize, leaving 3500-2500 = 1000 dollars leftover. This is the amount he donates.