Answer: Harder to sustain cooperation
Step-by-step explanation:
When the number of firms in an oligopolistic market increases as is the case here, cooperation becomes harder because profits become smaller so companies start to become more selfish.
Also in this scenario, the cheating firm has the incentive to do so because the profit is so much higher than sharing so companies will always be looking to cheat in order to make this profit. The other firms would reply by reducing prices and all of them would suffer.