Bipartite Graphs and Matchings · Hard problem

A wheel $W_7$ has a hub vertex $h$ joined to every vertex of a $7$-cycle $1\text{-}2\text{-}3\text{-}4\text{-}5\text{-}6\text{-}7\text{-}1$ ($7$ rim edges plus $7$ spokes). What is the minimum number of edges that must be removed so the whole graph becomes bipartite?