Eulerian and Hamiltonian Graphs · Easy problem

The Petersen graph has $10$ vertices and is $3$-regular: each vertex is connected to exactly $3$ others. The graph is built from a $5$-cycle (vertices $0,\ldots,4$), an inner pentagram (vertices $5,\ldots,9$), and spokes connecting each $i$ to $i+5$ (indices mod $5$). How many vertices of the Petersen graph have odd degree?