Tom Shanks Sign a Contract to Make a Film for GMG

Tom Shanks sign a contract to make a film for GMG Pictures for $20,000,000. The contract was not under seal. Part way through filming, he gets an offer to make another film for even more money, but production is starting immediately. He tells GMG he requires another $2,000,000 to complete their picture, or he'll walk. Is GMG legally bound to pay?

A) Yes. GMG cannot rely on their promise to pay $20,000,000. That is past consideration.
B) Yes. Preventing Shanks from taking the other job is restraint of trade.
C) Yes. Because the contract was not under seal, the consideration flowing from GMG was not valid.
D) Yes. Shanks can rely on the doctrine of detrimental reliance: he relied, to his clear ability to make another picture.
E) No. Shanks was given consideration to make the picture for GMG and has no right to demand more money now.