Suppose that Mr. Green Jeans sells $5,000 of wheat to Big Ben Bakery. Big Ben uses the wheat to make flour and then hamburger buns, which it sells to Hamburger Heaven for $11,000. Hamburger Heaven also buys $20,000 of beef from a rancher. Hamburger Heaven uses the beef and buns to make 10,000 hamburgers, which are sold for $5 each. How much do these transactions add to GDP?
a) $86,000
b) $50,000
c) $36,000
d) $31,000