Which of the following burs would you prefer to use preparing a slot for the relation of an extensive amalgam restoration on maxillary molar

Which of the following burs would you prefer to use preparing a slot for the relation of an extensive amalgam restoration on maxillary molar:
a- Number 5 round bur.
b- Number 56 fissure bur.***
c- Number 556 fissure bur.
d- Number 35 cone bur.