What is the solution for this question? This is from Dixie book- Optimization theory

Maximum Value Functions 67 Exercises Exercise 5.1: The Cobb-Douglas Cost Function Consider a production function n y = A I (5.22) j=1 where y is output, the r; are inputs, and A and the a; are positive constants. Let w = (w;) be the vector of input prices, and show that the minimum cost of producing a given output level y is C(w, y) = B(y/A)1/P ( w;la;) ailB, (5.23) j=1 where B = _; aj. If B