Make your step by step solution to formulate the given as a LP problem:

Miggy, a millennial health buff, is trying out a new diet regimen that would require him to have an intake of at least 60gms of protein and 30gms of fat per serving of a premix smoothie. Two premix concoctions are available and he needs to determine how much of each premix should he take while minimizing cost.

Brand A and Brand B are the two premixes. Brand A has 15gms of protein and 10gms of fat and costs 0.80cents per sachet. Brand B, on the other hand, contains 20gms of protein and 5gms of fat and costs 0.50cents per sachet.

How much of each brand of premix should Miggy take in order to satisfy his diet regimen while minimizing costs at the same time?

Formulate as an LP problem.