Frank Is a Loyal Employee Who Has Spent Much Time

Frank is a loyal employee who has spent much time above and beyond the call of duty promoting his employer's company on weekends.Frank's boss says to him,"Because of all this extra work you have done,you'll get a $1,000 bonus next month." Because of this statement,which of the following is true?

A) The company is not obligated to pay him because the consideration is past consideration.
B) The company is not obligated to pay because there was a preexisting duty.
C) The company is obligated to pay because Frank has performed the extra work.
D) The company is obligated to pay because there is an implied-in-law contract.