The waiters at Jim's restaurant, Gavin and Stuart, have been pestering Jim for weeks about getting an increase in their hourly rate. Jim repeatedly explains to Gavin and Stuart that he cannot agree to a pay rise without first speaking to his accountant, and that he will not have time to do so until the end of the month. Gavin and Stuart are becoming increasingly frustrated with Jim's refusal to consider their request for a pay rise. One Friday evening, during the busiest part of the shift, Gavin and Stuartconfront Jim and tell him that unless he agrees to increase their hourly rate by $5 per hour, they are going to walk out, leaving him to serve the customers on his own. Jim has no choice but to agree to their request. He promises to adjust their pay as requested. Is Jim legally obliged to keep his promise? Focus upon whether or not Gavin and Stuart have engaged in duress.

is this contract law?