$4.$ Router R$6$ advertises the prefix $172\mathrm{.}10\mathrm{.}3\mathrm{.}0/24$ using a routing protocol that supports ECMP. All routers are configured with an ECMP value of $4.$ All links shown in the diagram have the same cost. How many entries with a destination prefix of $172\mathrm{.}10\mathrm{.}3\mathrm{.}0/24$ are in router R$1$s routing table?a$.1$ b$.2$ c$.3$ d$.4$