n which ONE of the following situations was a VALID contract concluded?

1 Sally engages a professional seafood caterer to provide seafood for her birthday party, to which twenty guests have been invited. All the guests confirm that they will attend Sally's birthday party. The day before the party, ten of the guests inform Sally that they will not be able to attend the party because they prefer to attend a street party at the same time and date in Sandton.

2 Nicolas makes a new year's resolution and undertakes that he will save R500 each month by paying R500 into his savings account on the first day of each month.

3 Peter purchases a new pair of running shoes for R600 on the official website of Nike.

4Reeze undertakes to sell the moon and one star to Shana for R500.(2)