What is the difference between a mission and vision statement?

a$.$ The mission is the "when" and the "how", and the vision is the "why"

b$.$ The mission is the "what" and the "how", and the vision is the "why"

c$.$ The mission is the "why" and the "how", and the vision is the "what"

d$.$ The mission is the "where" and the "how", and the vision is the "why"

e$.$ None