Consider the history of exchanges as if it were described in two separate deals where:
In the first deal, the man buys the goat for $ 70 and sells it again for $ 80, so he gets a profit of $ 10.
In the second deal, the man buys something for $ 90 and sells it again for $ 100 so he gets a profit of $ 10 again.
Conclusion: the name gets a total benefit of $ 10 + $ 10 = $ 20.
Well...that's one way to look at it. Lol.
yes, of course I think that's the answer
The way I look at it, they guy lost $10.