Double check my answer and try to work it out, but this is what I did..
139 divided by 10 is 13.9, so about 14. so about 14 groups of 10.
so if they made 14 groups of their ten dollars, then the local business will contribute 50% of the 10 dollars made (5 dollars) for every time it is sold/gained.
so you will end up with 14 x 5=70. 70+139=209, which is less than 240.
So the answer is NO, it is not reasonable that they will end up with 240 total after the contributions made by raising 139 dollars worth of money.