Can 300 Reapers (Mass Effect) help in preventing the Fall of Reach (Halo)?

Scenario:

A mysterious rift in space-time opens, and 300 Reapers emerge near Reach. Instead of their usual destructive intent, the Reapers express an unprecedented desire to assist humanity in preventing the Covenant's invasion of the Reach planet.

Settings:

The Reapers arrive the 24th of July, 2552 just after Winter Contingency is declared and will cooperate with the UNSC and Noble Team.

300 Sovereign-Class Reapers led by Harbinger.

Can they succesfully repel the Covenant invasion?

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^(Note: This number of Reapers was given assuming the Covenant fleet was indeed around 300ish ships. If my numbers are off or too low , just scale the Reaper numbers up as well.)

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