The <singleton set> $\{\varnothing\}$ has cardinality one, so its <power set> has cardinality two. Taking the <Cartesian product> with the singleton $\{\varnothing\}$ leaves that cardinality equal to two. The outer power set therefore has \b[$2^2=4$] elements.

Solution

Past exam of the year 1 of the computer science course of the University of Oxford / 2017 / Discrete mathematics, continuous mathematics and probability / 1 / c / iii / Solution

 Solution (source code)