Solution: The cost of A is X yuan, and the cost of B is 500-x yuan.

( 1+50%)x * 0.9+( 1+40%)(500-x)* 0.9 = 500+ 157

1.35 x+630- 1.26 x = 657

0.09x=27

x=300

500-300=200 yuan

A: The cost of A is 300 yuan, and the cost of B is 200 yuan.