When the farmer sells wheat at $120, he pays a tax of 120*0.1 = $12.
In the next stage the trucker adds a margin of 10% and sells the wheat to the cookie company.
The taxes he pays are ($120*1.2*0.1) = 14.4
The cookie company adds a 40% margin and sells the cookies to the retailer. The taxes they pay are $120*1.2*1.4*0.1 = 20.16.
The retailer has a margin of 14% and sells the cookies to the customer. The taxes they pay are: $120*1.2*1.4*1.14*0.1 = 22.98
Therefore the total amount paid as taxes is:
12 + 14.4 + 20.16 + 22.98 = $69.54