The allocation where D1, D2, D3, D5, D6 consume and S1, S2, S3, S4, S5 sell is not
Pareto efficient because
a. D1 could give his widget to D7, and both D1 and D7 are better off
b. D6 could sell his widget to D4 for $5, and both D4 and D6 would be better off
c. We need every consumer (D1, D2, ..., D10) to buy and every seller (S1, S2, ...,
S10) to sell
d. D6 should not get to consume before D7
e. there will be a shortage of widgets