Sally Goes to Have Her Hair Trimmed and Agrees to Pay

Sally goes to have her hair trimmed and agrees to pay $40 to the stylist.While there,Sally decides that she would also like highlights.The stylist informs her that highlights will cost an additional $30.Sally agrees to the price,gets the highlights,but refuses to pay the extra amount.What is the likely result in a dispute between Sally and the stylist,and why?

A) The stylist will win because she did additional work in exchange for the extra payment; therefore,Sally's promise was supported by valid consideration.
B) The stylist will win because she did additional work in exchange for the extra payment; therefore,a valid unilateral contract existed.
C) The stylist will win unless Sally can show that she had previously received both a trim and highlights for $40.If she can prove that she previously received both for $40,the "past expectations" rule applies.
D) Sally will win because the stylist had a preexisting duty to have her hair looking its finest.
E) Sally will win because there was no valid consideration given in exchange for the highlighting.