BGP Local Preference

The route $6\mathrm{.}6\mathrm{.}6\mathrm{.}6/32$ is being learned via R$6.$ All routers are addressed with the interface IP relevant to the router. e$.$g$.$ all R$2\text{'}$s IP addresses will end with $.2$

a$)$ Suggest how to influence the routing decision on R$2$ to take the path via the longer AS path through R$4$ and R$5.$