The mass of the product of spheres (Q2260708)

The author expresses masses of the product \(S^2\times S^2\), the Grassmannian \(G(2,4)\) and the product \(\mathbb RP^2\times \mathbb RP^2\) (all these manifolds being equipped with suitable asymptotically flat Riemannian metrics defined outside a single point) as the sums of explicit infinite series and provides their approximate numerical values of them.