How to connect two ISP ?

I am trying to solve a study case for my college, but I got stuck in a point, maybe someone could help me:

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• c) The interconnection between the two ISPs is accomplished through static routing, configure.
• d) Inject the default into OSPF through PE5 and PE6. The PE5 should be the default GW of all ISP, in case of failure, the PE6 will assume this function.

This is my topology:

https://ibb.co/pvNXY5L

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Isp tier 2 uses rip as a routing protocol, and the orange"isp 1" uses ospf, my doubt is how I will configure static route to interconnect both isp ? should I configure a static default in orange isp and redistribute in ospf ? thanks a lot..