At what terms of trade (relativeprice ratio) could Wally and BigBlock specialise and trade with one another, so both end up with more bricks and barriers than they could have produced on their own?

Select one:

a.20 bricks per 1 barrier

b.25 bricks per 1 barrier

c.35 bricks per 1 barrier

d.45 bricks per 1 barrier

e.55 bricks per 1 barrier