~47.3 seconds later, another Le'Solar spawns followed by a General GreGory ~13.3 later.
3 more Le'Solars spawn in later with a 13.3 ~ 15.3-second interval. 2 more General GreGories spawn later with a 30 ~ 31.3-second interval.
First, save up money. Once GreGory is close, start spamming 3 of your 4 meatshields, Chill Cat, Can Can Cat and Seafarer Cat. Once GreGory is dead and the 2nd Le'Solar is close, deploy Awakened Bahamut. After he is dead, spam every cat you have, but don't drop your money below 4000¢. Stall until Awakened Bahamut has recharged. Once he has recharged, deploy him. he will take care of the level easily.
Guide video: https://youtu.be/5u9jZM48KdQ